happy life

I am a student who is learning studying (many people here misuse learn and study) mathematics . l like maths ('math' is not wrong, but it is American; British English uses 'maths') and l believe l will make it. What make me even more happy/happier is that l have a harmonious family .

happy life

I am a student who is learning mathematics.

I am a student who is studying mathematics.

l like math and l believe l will make it.

I like math and believe I will finish my degree/education.

I like math and believe I will get good grades.

what makes me more happy is that l have a harmonious family. <- You can say this in a better way.

Question: What makes you happy?

Answer: Having a harmonious family. 

Statement: Having a harmonious family makes me happy.

                   I am happy because I have a harmonious family.

                  I am happy becuase my family lives in harmony.