Is this sentence grammatically correct I am studying English twice a week or should it be study Or are both just in different present tense?

Both "I am studying English twice a week" and "I study English twice a week" are grammatically correct, but they have different meanings.

* "I am studying English twice a week" uses the present continuous tense, emphasizing an ongoing action. This suggests you are currently in the process of studying English and that it's happening regularly.

* "I study English twice a week" uses the present simple tense, indicating a habitual action. This implies that you regularly study English twice a week, but it doesn't necessarily mean you are studying at this very moment.

So, which one is best depends on the specific context and what you want to emphasize.