Re: I'm trying to download apps and a message of insufficient space keeps popping up.
1. NEVER use a "cleaning app". Most of them just kill apps that are in RAM, wasting time and battery. Most apps cclean up after themselves and nothing needs to be cleaned (except the cache).
2. Moving an app to the SD card doesn't always save any space. For each piece of the app that's moved (and how large the pieces are depends on how the app was developed), Android leaves a link in internal storage. If there are enough small pieces, moving the app to the SD card costs you space.
3. Deleting "stuff" only works if your phone is partitioned to use the same space for apps and "stuff". Some phones are, some aren't. On some phones, you can delete all your "stuff" (audio files, video files, documents, pictures) and still not have any space for installing apps, because apps are installed to a different place than "stuff" is.
4. If you have a large logcat file, deleting it can free some space. See
Low on space? Dump logcat.