Most definitely or if you don't want to do that, break up with her either way. There is no point living a lie and it is always best to nip it in the bud before it goes too far
If the man is really gay then he's gay and not interested in women so your girlfriend is safe with him and you shouldn't worry. However, your girlfriend still has no right to stay out all night with any man gay or not. You should communicate directly to her calmly that you would never do this to her (if you had a lesbian friend.)
Yes! You should tell her, you should also tell him how that made you feel. Think about it, you'd want to be told!!!!
no he has a girlfriend
tell him you love him if he says gross try to make a joke out of it.
Gay men do not have girlfriends unless they are closeted and hiding. In that case, a sham girlfriend is sometimes called a beard.
You can't tell. A gay man might let you know he is gay by acting in a stereotypical way, exaggerating his speech and gestures. But if he doesn't do that, then you can't tell.
There is no way to tell. you have to ask him.
The only sure way to know if anyone is gay would be for them to tell you, or for you to catch them in the act. If he's bi he can have a girlfriend or a boyfriend (he wouldn't "need both") and there would be no problem.
Ask him
There are not really many signs to tell you a man is gay. Some gay men do act feminine which is a clear sign.
The woman a gay man 'uses' as a girlfriend/wife in order to 'play' straight for the public.
The only time you should worry is if the guy she left you for is bisexual (likes both women and men and it is a conscious decision to be bisexual.) A gay man is simply gay and only interested in men, so that would mean your girlfriend had a gay friend and not a lover. If this is the case by all means take her back. If he is bisexual then you will have to communicate with her and hear her side of the story and then tell your side of the story as to how much she has hurt you and you and you will have to make the decision from there.