Weight training is hands down a must have in your training regime if weight loss is your goal. Weight training builds muscle mass and the more muscle mass you have in your body the higher your metabolism will function and the more calories you will burn.
Now there is a lot of misconception out there about the heavier you lift the better it is and I'm here to say not necessarily. If you are lifting heavy but your form is poor you will be restricted as to the results you will be able to achieve that's if you don't injure yourself first. In my opinion form and technique is everything and way more important than how much you can lift. Egos need to be left at the door.
When I work with my clients I firstly improve their posture, muscle imbalances and increase their core strength before even considering lifting really heavy. Without the proper foundation like I said before you will find you will get to a certain point and then you will be unable to go any further without injuring yourself, you will have to go back and revisit these foundation building exercises anyway. So why not do it properly from the start.
Like I always say slow and steady always wins the race. When you are weight training try to think about what muscles you are ment to be using and focus on activating those muscles throughout each rep. Its so easy to just go through the motions with exercises which is wasting your time. Focus on your speed also. If your goal is to increase muscle mass for example fast paced reps will not allow your muscles enough time under tension. Slow it down.
If everything is a race or a competition between you and your gym buddy best to train alone, if you are serious about getting results that is. Both guys and girls get to caught up in what everyone else is doing instead of focusing on your own journey. Everyone is different and everyone's bodies are different. There is no competition. The only person you should be competing with is yourself.