不怎么 (bùzěnme) seems to mean "not how", but it actually can mean "not often" when used together with a verb.
不怎么 with a verb
When 不怎么 is used with a verb, it means that one does not put a lot of time or energy into doing it. In other words, the action is done "not often." When the verb is used with an object, it also means that the number (or quantity) is really small.
subject+不怎么+verb
Examples
Tā bù zěn me xǐ huɑn shuōhuà.
他 不怎么 喜欢说话。
他 不怎么 喜欢说话。
He doesn't like talking too much.
Note that the last example uses 没 instead of 不. This is because the verb uses or implies 有 it uses the same the 有 negation rules.
Lastly, make sure to use 不怎么 with a verb if you want it to mean "not often". Using it with an adjective gives it a different meaning.
