Transmission shifting?

Hey there, I’m looking for an experience professional mechanic to answer my problem my mother doesn’t think I know what I’m talking about because I haven't been told by a professional.
Anyways, my transmission has a drive reverse park and 1 and 2 which I believe is used for hills and such but in my case my trans tends to slip or get stuck in 3rd and whatnot and it’s really wrecking my car so I’ve come to the solution to keep it in number 2 as it’s the one I use most, even though going around 50-60mph tends to burn lots of gas because its at a real high RPM, my transmission doesn’t slip doesn’t get stuck and it’s had zero issues using this method and then my brother thinks shifting into this gear is scaring him, and he says it’s loud and embarrassing, keep in mind my car is bone stock unless you count a stearin wheel cover and some pink seat covers. And he gets scared and complains all the time when my car makes a louder noise and my mom thinks using the number gears drastically destroys my car and that I should use this drive automatic. And she said that using gear one and two is strictly for hauling oversized loads on a hill.