Hello @alexandra_janos
Thank you for contacting the Canvas Community. We're sorry to hear you've been experiencing issues with exporting/importing item banks. Thanks for explaining the problem and we understand that it is a bit of a process to get question banks to item banks (currently) and will be working on improving that for the future. For now, there are some options you have but yes - you can continue using question banks without issues. Ideally, the process to transfer question banks to item banks will be as intuitive and easy as the "migrate" option we have now to move classic to new quizzes. You are welcome to continue using question banks for now.
To convert question banks to item banks you have some options as has been discussed in this post here:
https://community.canvaslms.com/t5/Canvas-Instructional-Designer/Transfer-from-old-Question-Banks-to...
You can migrate the classic to new, and then move those to an item bank. You can export the classic quiz as QTI file and then import as a new quiz (probably best method) and create the item bank when you do so. There's some good directions in that post, feel free to check it out.