Sakarmak kriya is a "bhed" of kriya where two kriyas exist in a sentence .
for example- ram khana khake so gaya.
here you can see 2 kriyas - khake(eat) and so (sleep).
in akarmak kriya there is only one kriya in the sentence.
for example- ram khel raha hey.
here khel(playing) is the only kriya taking part in the sentence.
hope i helped ye.