Files keep crashing

I am surprised that after already a couple years of this same question being asked this is still happening. I have and own an ipad pro for years and upgraded less than a year ago. Everytime I open a pdf and use to markup it'll crash. I have to constantly press done and close then reopen every couple of minutes to save my marks because I am never sure when it will crash and erased what I have written. I do not understand how this problem has continuously been persistent with the apple files app and nothing has been done about it to improve. Is using an app better than using apple supported products? Why have it as an option to use when you open files if it doesn't work effectively?

As a teacher who is trying to give immediate feedback to presentations or writings, using the apple "supported" programs would be better and easier but it seems like there is probably something better to use than depend on Apple for such productivity service, is that still the case? Is it better to use another company's App to do what Apple cannot provide with its "universaltility" of its programs?

Reading responses from before it sounds like it is the case. If it is, which is the best one that saves as you continue to work on the document instead of apple products behaving as I have 1st generation iPad? Please help as I am tired of losing work and having to also taken random screen shots to remember what has been written before as the dependability of Files is terrible.