First week in the gym

So this was my first week in the gym and I be loving it but I have some simple questions. So this week was the first time I really ever lifted weights I’ve always done push ups and dips so I’m not really adjusted to weights yet. Now my questions are

1.why when I do a weight that should challenge me I can’t do it strict form so I lower the weight, then after my 3 sets I don’t feel any kind of fatigue on the muscle group just the surrounding muscles.

2.why when doing dumbbell bench press I had to lower the weights to 20 pounds bc my arms where waving all over the place and I couldn’t keep the movement controlled.

3.why no matter what I try I can’t feel my lats in any way.