Newbies--be careful with this device

Be careful with this X Max II Pro device, especially if you are new to vaping--the lack of instruction and documentation is something to be really concerned about. I bought this device because I read vaping flower would be healthier than smoking during Covid 19. I read many of the reviews at this site and other sites, and someone suggested this device to me instead of higher priced alternatives. I started using it on an every day basis on 2 May. On 23 May after three weeks of consistent usage, I developed this scary sensation in my chest (I had previously been consuming via combustion on a very regular basis for 19 years and I NEVER had a chest or lung issue). I stopped using the device immediately and the chest sensation went away in 48 hours. I have been very frustrated with the little documentation that came with the device, especially the instructions for proper use. After reading up further on the device in the last week, I have learned that many people “sterilize” it by running it on its hottest cycle of 428 deg F for at least three sessions to “burn off” any thing remaining from the manufacturing process. This was never in the instructions. This would have been very helpful to know before consuming via the device. I hate to think which chemicals I was inhaling because I didn't know to perform this step. Also, there is little instruction on how to properly and safely use the device. I had been filling up the chamber about half to 3/4 full before using. Is this enough? How fine does the flower have to be? I did not know any of this because it wasn't in the instructions. What are the advantages or disadvantages of consuming on any of the temperature levels? I have no idea, it is not in the instructions. How do I know when the flower has expired and can no longer be consumed? I have no idea, it's not in the instructions. The bottom line is that I'm not sure, despite all the glowing recommendations, this device is safe for human usage. I do not trust this device not to give me lung or chest issues and during Covid 19, that is REALLY scary.