guys... help me pls

my J7 always need to clear the RAM at smat manager
when it shoot up to 80%.. it will hang if not clean up
damn annoying... every time I have to clean RAM after scroll fb for about 10 minutes or play a short youtube video

whenever after cleaned = RAM used show 50%~60%
use few minutes it jumps to 70~80% .. then hang

last year went to Samsung service centre... complaint .. they simply format my hp
WTH !! I lost so many important data inside... but prob still unsolved