I have A50 and i always have problems with internal storage space. It always full and i could not move the files to drop box or Google drive and Samsung cloud has 15 G space which is really nothing for me and you can not upgrade it to higher capacity plans.
Please advise me a solution.
My phone is really slow and i can't update it without deleting some data
I agree with @Master_g321 , have you inserted a micro SD card yet? You can have almost up to half a terabyte of storage with the A50 if you really need the local storage using the expansion slot.
And I suggest you try to sort out your apps and files using space saving apps or manage your files just so you can delete the things you don't need.