After school

I am an alumni. I had written all my exams (/ I have finished all my examinations.) Now, I have to choose a path for life, but I can't imagine what it could be. When I was 5 years old, I wanted to be a nurse or a dentist. Now, I have grown (/ I grew)  up and I don't know who I am. Or which profession I must choose. I would like my future job to earn plenty of money. But both these qualities are too seldom nowadays.

Man:  I am an alumnus.

Woman:  I am an alumna.

Plural for a group of men:  We are alumni.

Plural for a group of women:  We are alumnae.

Plural for a mixed group of men and women:  We are alumni.   OR     We are alumni and alumnae.

HOWEVER, when the words "alumnus", etc. are used, you should mention the particular university.  Example:  I am an alumnus of Stanford University.

If you don't mention the university, it is more usual to not use the words "alumnus", etc. and instead refer to yourself as a graduate, or use the verb "graduate":  "I am a college graduate."  "I graduated from college."  I graduated from a university."  

After school

I am an alumna. I had written all exams and I have to choose one way in to life but I can't imagine what It could be. When I was 5 years old I wanted to be a nurse or a dentist. I grow up but I don't know who I am and which profession I must choose.
I wanna like my future job and get much money. But both these qualitiesare too seldom nowadays.