Nissan 2017 Sentra Acceleration/RPM issue

My nissan will hit 2000 rpm which averages around
65 to 70 miles and hr. The car wont accelerate. It is
as though the gas is not pressed then it will kick in
and engage. As speed increases it will do it
intermittently. I heard CVT transmissions are
overheating and using up fluid causing it to skip
and without going to dealership to have them add
fluid, one cannot check the fluid themselves. I am
wondering if I jist changed the fluid if it would help.
Or is it the throttle body?
The air filter has already been changed. Any
suggestions? I took it once to the dealership and
they updated the software but did not fix the
problem. They said it never threw a code and so
diagnostic machine wouldnt pick up the problem
and when driving they could not recreate the issue.