The HDD space that Opera can occupy is absurd. Even deleting the cache or temporary files, so much waste is accumulated that right now the space occupied in the different directories is almost 5.5 Gb. Absurd. Also, there are too many directories for Opera to function.
I love their tiles as a home page and also I don't want to be a Chrome user, but maybe it's time to look for options. Opera isn't even the fastest, Edge beats it.
You should be able to schedule a cleanup, perhaps weekly, or limit the maximum space reserved for Opera.