can you lose weight by doing exercises with dumbbells

Not likely. Cardio is best for losing weight and also cutting calories.

You'd have to work more than just one muscle group in order to see weight loss results.

Burning more calories than you consume each day, is the only way. Exercise burns calories, so
you can eat more, but some people also get hungrier the more they work out. You should try for
500-1,000 calorie deficit each day. You will need to count calories, and track your calorie burn
with a fitness tracker. It's kind of a pain at first, but once you get with the program, you will
know how much to eat each day, and it will get easier. Stick with it, it won't happen quick,
but it WILL happen, if you put forth the effort. It will be worth it. Good luck.

Possibly a little, if combining it with a decent lean diet. The main thing that contributes to weight loss, is eating less aka a calorie deficit. You could sit most of the day, eat very little and you would lose weight. But exercise is good!