1) I graduated from college
- Nakapágtapós ako ng college/colehiyo.
- Nakatápos ako ng college/colehiyo.
You may hear us saying it either way and it’s possible that some may use “sa” in place of “ng”. The translation would actually be, “I completed/was able to finish college”, but that’s how we would usually say it. With our tendency to use some English words when we speak, it would not be uncommon to replace “tapos” with “graduate” and come up with “nakapag-graduate” and “naka-graduate”, as si_kano used in his answer.
2) I am going to graduate from college
- Makakatápos ako ng college/colehiyo.
- Matatápos/Makakatápos na ako ng college/colehiyo.
The 2 sentences are the translations, but would depend on the intended meaning. In the first one, the speaker is making a promise to himself that he will make sure he’d graduate from college. In the second one, with the addition of “na”, the speaker is saying that in the near future, he will be graduating from college.
3) I am going to come back/go back to the Philippines next week
Babalik ako sa Pilipinas sa susunod/darating na linggo. (It is also possible to say “sa linggong susunod” or “sa linggong darating”).