Underweight situation. How to gain? Are these tests accurate?

I have weight problems. I eat 3 meals a day, fruits and stuff but i can't put on on weight.
I went to a HerbaLife center and i took one of those test that puts on you a scale which sends a small electric current through your body. they find out: muscles %, fat %, water, calories you burn, so on.
Based on that he told me i need to eat 130 grams of proteins a day and i'm nowhere near that.
is he just trying to sell his protein shakes or might that be accurate?
i can't eat that much protein as i have a tricky stomach.
Any tips on how to gain?
Updates
+1 y
And as far as i knew protein shakes aren't that healthy either. Plus my stomach is already in pieces...
Underweight situation. How to gain? Are these tests accurate?
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