any idea on dealing/controlling teenagers in classroom?

I recently joined a school as a teacher. Most of the classes I take are manageable, but one class. The class has 25-30 students (ages 14-16). My class is usually in the last period, so the students are tired, as I am too. They show little interest in class, do not pay attention, and I find it difficult to explain the topics because they are constantly talking to each other. I tried being the strict teacer, I think it is not wirking. Looking for ideas to make them more interested in class.

ps: The subject is pretty easy, but they are not interested, so they feel it is difficult. I feel that if they bond with me, they will listen to the explanations, and the subject will become easy.