understood this part now. thanks a bunch for that!!
so now it's like this:
now the main question is about why "Lift=/ mgcos20"
they are opposite to each other. so why should we not do:
Lift= mgcos20°
and get the value for lift instead of finding the value of lift force by doing:
lift x sin(70°) = mg
if i'm not wrong, i believe you've already explained that, so if you don't want to anymore, it's understandable. thank you still for helping!!