A new skill to add to working forwards from the "to" form. If you hear or see a word like vamos, get into the habit of working backwards from it to build the other versions.
vamos → strip -amos → va, vas, van
You do not need the "to" form to do this. The -amos already tells you your vowel is /a/, and that is enough to go on.
Va · Vas · Van · ¿A dónde vas? (to where are you going)
The "to" form of to go is ir, i-r all by itself, so it is very irregular. The reason is historical: two separate verbs stuck together over time to form one.
Ir comes from one verb, and the other versions come from a different one, which is why an -ir verb has an a turning up throughout. The related French aller gives English alleyway.
Quiero ir · Puedo ir · Debo ir · Tengo que ir · Tengo que ir ahora
If you know Italian or another Latin language, the same splitting is visible there, and noticing it helps you internalise the Spanish word.
With bien you lose the final e and the middle e splits.
Words ending a are feminine, and -ión and -idad are feminine endings. But a word ending in e tells you nothing: there is no way to know from the word itself.
You have to look it up, or look at what is around it. Hearing esta noche in conversation, the a on esta tells you noche is feminine.
Tengo que ir esta noche · No como carne · No como carne y no tomo alcohol · Como carne y tomo alcohol
Remember the h in alcohol is not pronounced.
Worth keeping straight, because the English blurs them. Debo ir is I must go. Tengo que ir is I have to go, and it is que added to tengo that shifts the meaning from possession to obligation.