Hi @gift79649
Use the Samsung ''My Files'' app to manage which files you want to delete or keep.
See p.73 of the [https://ss7.vzw.com/is/content/VerizonWireless/samsung-galaxy-a12-ug|user manual].
Also the phone supports micro SD cards having a capacity of up to 1TB i.e. 1000GB, so inserting a card with a higher capacity than what is already inserted might be an option if you wish to keep all of your data and add more as well. If you need more than 1TB of additional storage space then maybe a phone is not the best option.