Since I have starting making my website I managed to successfully upload around 50 media (mostly images) before it started to give me errors, almost always this one:
"Failed to write file to disk"
Via FileZilla I managed to change the permissions of wp-content - uploads file (both files and directories) which all the forums say should solve the problem but it doesn't. I called with my hosting provider and to ask "if they can clean the temporary folders" which is often suggested, but they didn't see a problem with that and suggested that the problem is with wordpress or laytheme. Also I didn't exceed the quota of my webspace.
I genuinely don't know what else to do so if anyone could help would be amazing.