Job versus work.
It does sound weird to my ear but I have no idea how to put it right.

"How many jobs have you worked before" or "How many works have you worked before" or "How many jobs have you done before".

which one is more grammatically correct?.

Also, I wonder how do you say it in English when you saw your friend was over there and then you suggested your other friends to go meet that friend: can I say: "let's go to his side" or "let's go meet up with him" or "let's go say hello to him".

Thanks in advance.

Question

Job versus work.
It does sound weird to my ear but I have no idea how to put it right.

"How many jobs have you worked before" or "How many works have you worked before" or "How many jobs have you done before".

which one is more grammatically correct?.

Also, I wonder how do you say it in English when you saw your friend was over there and then you suggested your other friends to go meet that friend: can I say: "let's go to his side" or "let's go meet up with him" or "let's go say hello to him".

Thanks in advance.

Answer

I'd say "How many jobs have you had" if I was making a general question and I wasn't concerned whether you were working now or not. If I particularly wanted to know how many jobs you've had before the one you are working now, I would say "How many jobs have you had before". That's just my preference.

For your 2nd question, "Let's go say hello to him" is perfect. There's lots of variations of course. Myself I'd probably say "Let's go and say hi to him" I'd say the name of the person, though and not "him" if it was a mutual friend.

Answer

How many jobs have you had. (The 'before' is redundant. )
Let's go over and say hello.