I understand it's a very stupid question, but l really need to master the skill of cleaning of my device very frequently, as this is the only one l have to do all of my work. Here's the current available space :
You can use adblockers like this one: https://play.google.com/store/apps/details?id=dnsfilter.android
Not loading ads is one way to speed it up. Another is to use Firefox alongside Ublock-origin for websites. Your storage will take a small hit. Firefox can also be slow on low end android phones. Which is noticeable since its not as optimized as chrome on android.