So I've been strict on this keto diet with a friend of mine.

I'm not a doctor but yes it's normal for a little while. You need electrolytes and plenty of water, when you're keto you lose electrolytes faster because carbs hold on to those more so than fat. Potassium, sodium and magnesium. There's a multitude of ways to get these in. There's supplements but also some foods have them, you may just have to adjust.