Sorry to hear about the trouble. Regarding the first issue, that generally happens when there is no selection or no artboard has been selected. Regarding the second issue, please share a few more details like:
The version of XD and OS.
Have you noticed any specific pattern for the crash? Like does it crash while performing any specific task?
Does this happen on a specific file or multiple files?
2. Crahes happened in different situations and haven;t some specific pattern. I think I have a file with many variables and components and file size is too big - 30-40 Mb sometimes. Sometimes crashes happened when I switch-on my desktop from sleep, sometimes when I just worked.
3. It is not specific file. It was all different files.
So first issue happens when file was loaded and I haven't worked with him yet.