Do you have any instructors to guide you?

Your legs needs to be strong when you are swimming freestyle.

Firstly for your breathing, its hard to breath if your kick is not strong.
Second is when we breath for freestyle, if the kicking legs are not strong, we will sink abit.

As for a beginner for freestyle, i can suggest dont focus on swimming stroke first, can swim and breath for 2 to 3 times is consider very good d. Then slowly from there, you can pick up your pace, abit of stroke correction.