Go to Setting>General>Storage to see if you still have used up your iPhone storage. And check out what is exactly using up your storage.
Then try to delete the apps which occupy too much space of your iPhone, so as to get some storage back. If the deleted app is really necessary, you can reinstall it. Via uninstall and reinstall, you'll clear up the app caches and other related documents & data. Just like my Wechat, the apps itself only occupy 130MB, however the document and data could be 6GB after 1 year without cleaning caches.
Well, you may fell too trouble to clear up apps one by one, then you can try to use a iPhone Cleaner Software to do it easily. I got a such software at only 9.95$, named[https://www.imyfone.com/iphone-space-saver/|imyfone umate iphone cleaner] , it can clear up junk files, temporary files, hidden documents and data, mass delete apps/photos/videos etc. Maybe you can have a try, as it have trial version, you can use trial version to see if it really works.
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