가다 is just basic form of 'go' but it is rarely use and 간다 means 'go' or 'will go' ex) 나는 학교에 간다 (O) 나는 학교에 가다 (X) and 나는 학교에 간다 means 'I go to the school' or it's mean will go so you want strictly say go now -> 나는 지금 학교에 간다 will go tomorrow -> 나는 내일 학교에 간다

I thought that 가요 is common present tense, so i can use both ? or how it works, its confusing. Thank you

ㄴ다 makes an action verb into the present tense. 가다 is a basic form which is found only in dictionaries, so you add ㄴ to the verb stem(가- in this case). Be aware that the Korean language uses simple present tense for things one is doing *right now*. 집에 간다. I'm going home. 독일어 공부한다. I'm studying German.