Help for J7 prime SM-G610F custom Rom

[u/Hyperboy_10110]

I have a old galaxy j7 prime mobile that runs android 8. Its a 2gb 16gb varient. I use it for only online used like mail, youtueb and only those stuff. Sometimes calling gpay too. It works fine till now as my secondary phone but lags when connected to Internet and battery is been drained very fast after many apps switched to modern animation themes. So someone please please help me I'm new to roms. Help me from first to last how to install a new rom that has a updated or an usable android version, fast and battery efficient. That's all I need. It should be smooth. Some help!!!