As said in the title, Krita does not want to let me create a new brush... It closes every time I press the create a new brush button.
Is there a way to fix this...?
Also every time I perform a task, like making a filter layer or mask, there are random lines that appear on my painting...
Someone, please help me

For the first, it sounds like it is crashing. The second needs some images.

For the first, try to get a backtrace, then report a bug for that on bugs.kde.org in the product Krita with the resulting log file. That gives us a peek into what Krita thinks it is doing at the time of the crash.

For the second, report a separate bug, and attach a screenshot.