Hi everyone,
I have a question. Right now I'm an L1 visa holder living and working in US and at the same time I'm engaged to us citizen. Do I need to file any additional paperwork for our marriage and how can I become a citizen too or get the right to stay here if I would want to get rid off my L1 visa status?
I'm not sure how it works and if I need to leave the country. I would really appreciate your help.

after you get married, you would be applying for permanent residence, not citizenship.

Your spouse files the relative petition and you file the adjustment of status concurrently. At the same time you file for an EAD and advance parole. The EAD allows you to work for anyone in the US and the AP allows you to travel and return to the US to continue your PR application. You will not need to leave the US to apply for PR.

You will be scheduled for biometrics (fingerprints and digital pix), then for the PR interview. If you are married less than 2 years at the time of interview, you will be granted conditional residence. This requires you to file a petition to remove the conditions 2 years from that date.

I trust this was responsive to your inquiry. Congratulations and good luck.