Trouble Fixing errors

Dear person reading

I am working on a project for a friend, but my model is still having alot of small troubles when I review it in Cura. I have no idea how I can fix them and it would be amazing if someone could help.
It's not a super big model but it's just stressing me out alot....

If anyone is interested in checking and or maybe fixing the model for me, I can always send some money.

Thanks in advance <3