Learn Portuguese (Portugal): Nós seguimos o autocarro.

It can actually be both! For -ir verbs like seguir (to follow), the 'we' form is exactly the same in the present tense ('we follow') and the simple past tense ('we followed'). You have to rely on context to know which one is meant.

Do you pronounce the 'u' in seguimos?

No, the 'u' is silent. In Portuguese, when gu comes before an e or an i, the u is just a helper letter that makes the g sound hard (like the 'g' in the English word 'geese'). So, seguimos is pronounced with a hard 'g' sound.

I have seen the word 'ônibus' for bus before. Why is it autocarro here?

Ônibus is the word for 'bus' in Brazilian Portuguese. Since you are learning European Portuguese (as spoken in Portugal), you will use the word autocarro.

Can we drop the nós and just say Seguimos o autocarro?

Yes! Because the verb form seguimos is only ever used with 'we', the word nós is optional. Portuguese speakers often drop it unless they want to emphasize that we (and not someone else) are following the bus.