You must be practicing dumbbells in the wrong way. The best way to practice chest muscles is barbell bench press. If there are no conditions, it is push-ups. Then stretch the chest with dumbbells and expand the chest.

Wide-distance push-ups are mainly aimed at pectoralis major, but you can also practice the inside of the chest through narrow distances.

There are 4 groups and 30 groups every day, and you can rest for 30 seconds.

There is a video on the internet that seems to be 12 minutes to practice chest muscles. The effect is good. You can go and have a look.