Welcome, Kat. You'll find that there are a number of folks here who are more than willing to help.
When you post a request for assistance, it is important that you include the exact Mac model you have, and the exact Mac OS you are using. Also, let us know if you have ever done any disk cleanup/maintenance/repairs from a software perspective, ie, you used software to help with those tasks (and also if you did any of that on your own). And so, so important: hopefully you are making backups to an external device.
You're most welcome! And don't be afraid to ask anything? Believe it or not, even some "simple" questions and/or "simple" solutions can be a learning experience for anyone. I know I have learned some things myself that are so, so beneficial.
Excellent to know, thanks for your encouragement! I just posted my first thread, and ... well, it's complicated! But I'm hanging in there, at wit's end. I will solve this problem and leave no stone unturned, haha! ;-)