Image copyright Getty Images Image caption Mr Trump has been forced to reassess some promises since taking office

Being the president of the United States is not an easy job, as Donald Trump has quickly learned.

In an interview with the Wall Street Journal this week, the former businessman said he'd had to adapt from his deal-making background to the presidency.

"The magnitude of everything is so big, and also the decisions are so big. You know, you're talking about life and death," he said.

In his first few months, the candidate who offered simple and clear solutions on the campaign trail has had to deal with some complicated obstacles - and row back on promises.

North Korea's nuclear threat 'not so easy'

In that interview with the Wall Street Journal, the president revealed that during his first talk with China's President, Xi Jinping, he discovered China could not simply deal with the nuclear threat from North Korea.

"After listening for 10 minutes, I realised it's not so easy," the president said. "I felt pretty strongly that they had a tremendous power over North Korea. But it's not what you would think".

Image copyright Reuters

That exchange has raised eyebrows in some quarters.

Vox writer Zack Beauchamp observed: "Trump thought China could fix North Korea until the Chinese president politely informed him that North Korea is in fact complicated." That amounted to "basic facts... he could have Googled", Beauchamp added.

The same interview revealed that Mr Trump will not label China a currency manipulator, as he had promised, and had offered to make concessions on trade - another issue he has been vocal about - in exchange for help with North Korea.

Healthcare is 'so complicated'

The Affordable Care Act - or Obamacare - was one of Trump's major campaign issues.

"On day one of the Trump Administration, we will ask Congress to immediately deliver a full repeal of Obamacare," a statement from the campaign in early 2016 said.

That did not happen.

Media playback is unsupported on your device Media caption Trump's battles with Obamacare - in his own words

It took until March - two months after inauguration day - to bring a bill to the Republican-controlled Congress, where it was was rejected by Trump's own party.

He could not get the votes from Republicans, and withdrew the bill at the last minute.

"It's an unbelievably complex subject" the president said in late February.

"Nobody knew that healthcare could be so complicated," he added.

'Getting along' with Russia

During the campaign, Mr Trump repeatedly said he wanted to forge a better relationship with Russia.

He also tweeted that "both countries will, perhaps, work together" to solve global problems once he was president.

As late as November last year, after his election victory, he told the New York Times: "I would love to be able to get along with Russia and I think they'd like to be able to get along with us. It's in our mutual interest."

But the diplomatic reality has proved much more difficult.

Media playback is unsupported on your device Media caption Rex Tillerson: relations are "at a low point"

Mr Trump has launched military action against Russia's ally, Syria, and the US ambassador to the United Nations accused the Kremlin of sheltering Syrian President Bashar al-Assad.

A week later, Trump told the media: "right now, we're not getting along with Russia at all. We may be at an all-time low in terms of a relationship with Russia. This has built for a long period of time."

The wall (or fence)

Donald Trump's border wall was one of his most high-profile promises. He rejected the idea of using fencing, and insisted he would build a real wall from border to border - and make Mexico pay for it.

Mexico, perhaps unsurprisingly, refused to pay for the wall, which is estimated to cost anywhere from $10bn - $25bn.

In signing an order to start the process, Mr Trump accepted that US taxpayers will have to cover the initial funding - but says the money will be somehow recouped from Mexicans.

Image copyright Twitter

Quite apart from the political difficulties, there's another problem - an engineering one.

Mr Trump insisted, repeatedly, that he was not promising a border fence, but a "impenetrable, physical, tall, powerful, beautiful, southern border wall."

But the border runs for some 1,900 miles (3,100 km), over mountains, valleys, and rivers.

The bidding process is still in motion, and Trump has said costs will go "way down" once he turns his attention to it.

But on the sidelines, the administration's top immigration official, John Kelly, has been saying something different.

"It's unlikely that we will build a wall or physical barrier from sea to shining sea," he said in April.

Nato problem

Mr Trump's complaints about the Nato military alliance being "obsolete" caused much concern following his election victory.

He questioned Nato's purpose, while repeatedly saying that the US was paying an unfair share - all of which alarmed the other allies.

But Trump's new defence secretary, James Mattis, moved to calm worries after his appointment, calling Nato the "fundamental bedrock" of co-operation.

Media playback is unsupported on your device Media caption Trump changes mind over Nato

The president himself seemed to follow suit in April, when he hosted Nato Secretary General Jens Stoltenberg at the White House.

He declared that a renewed focus on fighting terrorism, as he saw it, meant Nato was no longer "obsolete" - but he still hoped other countries would contribute more.

Change of mind

On top of the learning curve Trump has faced in his new role as president, there are some campaign promises he simply rowed back on between winning the election an his inauguration day.

Chants of "lock her up" at his rallies were encouraged by his promise to prosecute Hilary Clinton - a policy quietly dropped to let Mrs Clinton "heal".

Policies on torture, climate change, gay marriage, deportation, and the banning of Muslim migrants were all softened and changed in the months leading up to his presidency.

Read more: Trump's promises before and after the election

But there is one clear area where Trump's shift in approach based on new information has paid off politically - his approval of strikes in Syria.

Media playback is unsupported on your device Media caption How has Donald Trump's position on Syria changed?

Four years ago, when military strikes against president Assad were considered by Obama's administration, Trump criticised interventionist foreign policy.

"Forget Syria and make America great again!" he tweeted.

But when children were caught up in a chemical weapons attack, he ordered a missile strike on a Syrian government airfield - a move applauded by politicians across the US political divide.