Above poster is right, if you don't know how to use these things at all, go see someone who can show you.
It often happens when you treat your phone like a computer
, phones aren't made to have 100 apps.
In settings you can reach your applications, and delete (clean) them. I don't know on iphones, but on my android you can see the state of the RAM in task manager. That said, it can be tricky, as the state of the RAM can "extend", showing more RAM than there actually is, you have the impression that you have enough of it! Of course it doesn't expend, and it becomes squeezed and so, unstable, just like the time and space continuum when my partner squeezes one out.
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"Ever since I was a child, I’ve never allowed myself to get too close to people. I’ve avoided emotional attachment. Perhaps I’ve been so afraid of death and dying that any connection just seemed like a bad thing, something that wouldn’t last." Dana Scully - Christmas Carol.