Hi there, @JonasPrida ...
Canvas actually has a built-in link checker that will tell you if it finds broken links, images, etc. It even will let you know if those things are pointing to other courses and need to be fixed. I'm not sure if you've seen this particular Guide, but I'll provide you the link here:
How do I validate links in a course?
Be sure to look through the examples in the Guide to see what kinds of things the validation tool checks for...so know how to interpret the issues that it may find in your own course.
I hope this will be a good starting point for you. Let Community members know if you have any other questions about this...thanks!