Has adolescence arrived?

We have an adopted dog who is approximately 5-6 months old (it is not known exactly, but almost all of her baby teeth have already fallen out). Recently there have started to be changes in his behavior, he has become much more vocal and has started barking at friends who come home or at people he sees coming into the doorway at night (she didn't do any of this before). We live on the ground floor of an apartment building, so we hear a lot of noises but until now she hasn’t reacted to them. He challenges us much more, and unless she is very hungry or there are treats in sight, he has a hard time obeying. Yesterday she started kicking the feeder with the feed, and until he threw it all on the ground and made me see it 😂,she didn't eat it.

We are first-time parents, we have lived with adult dogs a lot but we had never raised a puppy. Is what I see the beginning of adolescence? I just want to know if this change in behavior is more or less normal and I should just be patient, or if I should be worried. He eats and goes to the bathroom normally, he has energy, he doesn't seem to feel bad. Thank you very much in advance.