MacBook Air

go to Activity monitor>memory

you can see graph on bottom of the page

red circle is how much memory you have

black circle is how much memory you used

it's good until black circle comes to 7,5 or 8GB of memory

up there are programs which are running

quit only APPS NO TASKS!!!

put it on a hard surface and close the apps running on the background then turn the system off and wait for it to cool down