correct it plz

[sitasma]

we were there for 3 days and had some reason so

[emsr2d2]

we were there for 3 days and had some reason so

This is not a complete sentence. What did you mean?

[Nightmare85]

**Neither a teacher nor a native speaker.**

We were there for 3 days and had some/a reason so for that.

In my opinion "a reason" sounds better than "some reason", but both should be correct.
emsr2d2 has already mentioned that it's not a complete sentence.
Now (with my changes) it's a complete sentence, however, I don't know what you actually want to say.

Cheers!