Can I change my visa to an ausbildung visa ?

Check with the German embassy, or the Auslaenderamt (foreigner office) of the town you intend to live in. They should be able to give you the correct answer.

Hello, I come here to Germany to do ausbildung, but my language isn't good, which makes me to get probozeit kündigung. I was planning to do studienkollege after 1 year ausbildung but, it didn't happen so can I apply for FSJ in order to improve my language?

@supriyaghimire481 I think the best way to improve your German is a language course.

@beppi I can speak well German, it's not only language but also experience because I know I want to make my career in the field of Medicine. I just want to know, if it's possible

Has anyone done that before?

This subject has been covered extensively on this site. To study medicine in Germany is VERY competitive and only taught in German on a C1 level. One has to have the equivalence of the German Abitur and nearly perfect grades and recommended having a strong STEM cell background. Few foreigners have the requirements. 

@supriyaghimire481 Even your English needs improvement (judging from your posts) - and you wrote earlier that your German is not good and you lost a job due to this. The main purpose of a Studienkolleg (and a language course) is improving the language - so please consider that first!