hi mate,
in this case i would suggest a spring clean of your phone as appears that you have accumulated a lot of stuff over the years (i may be wrong here, so kindly correct me if i am). Check via Nokia Suite if there are any firmware updates available for your device, and update to the latest version offered. Then backup your personal data and perform a three finger hard reset. You will need to re-install all your applications and the such, but your phone performance will be much improved.
Also invest in a microSD memory card if you haven't done so already, and to install apps on the memory card rather than the phone, to save precious memory.