my trainer said that i have good stamina, but i dont have power is it true?

Your personal trainer is a professional and more knowledgable than anyone here, so ask them.

You are always weaker before you get stronger.

It's normal to feel "tired" while you are lifting weights. You are supposed to overload the muscle until it feels fatigued so that it can get stronger.

If your trainer is making you do high reps with lighter weights, you are toning the muscle and the faster and stronger your muscles get at repetitions, the more you will be able to do.
Every time you work out you should be able to add a few more reps IF you are getting enough rest inbetween workouts. You should NOT be working out the same muscle every day, or it will just get weaker and will never get stronger. Muscles need rest in order to repair, that's what makes them stronger.

If your trainer is getting you to lift heavy weights for low reps (8-12) and only 2 or 3 sets, then you are basically heavy weight lifting to gain muscle and you really need to overload the muscle, so feeling the burn is really important here. It should feel difficult, but you should be able to complete your sets by yourself. If you can't complete it you need to go down to a lighter weight. It's important to have rest days after you heavy weight lift.

Everyone needs cardio, to keep the cardiovascular system healthy and strong. Your lungs and heart seem like they are in good shape, so you probably don't need to focus on cardio as much as other people do. I wouldn't do an hour of cardio on the same day as a weight training session though. It's pretty standard to do a 10-20 minute cardio warm up before weight training (some people prefer to do it afterwards). If you do cardio after, you will have more energy to put into the weight training session, so it depends on which is more important to you. Cardio seems effortless to you, so the order probably doesn't matter. You are fit enough to try HIIT.