I had a lot of job since when I was high school. = I had a lot of jobs since I was a high school student.



When I was high school student. = When I was a high school student,  I worked at hamburger franchise.

Also I had a lot of part time job, delivery service, serving, cleaning, selling, ...

After graduated from college, I began work immediately at telecom contractor.
 = After I graduated from college, I began to work immediately at telecom contractor.

My first job was drew a floor plan page. but boss was very weird. so I quit this job.

Next company was Interior design company, I use to draw images by computer programs.

Now I working in here, my father's company.= Now I'm working in my father's company.