Almost 1 month. My biceps training method is to sit down and lift 8kg dumbbells with one hand, but it doesn't feel big enough. How long will it take to be obvious?

It is necessary to warm up before doing any exercise, which will help prevent muscle strain. As for your biceps, I think there are two main reasons. First, dumbbells are a little small, so we should increase the weight in a month. Moreover, muscles are a whole system, and you can't exercise only one aspect. You have to combine the biceps brachii with the upper body muscles to get a good exercise effect.