Hello and welcome to Healthcare Magic. Thanks for your query
Pulling back the foreskin or not before having sex does not matter as during entry into the vagina and intercourse, the foreskin will automatically get retracted back.
Regarding your question about
masturbation, this is considered as a normal part of human sexual behaviour and is very common in males of your age group. Masturbation does not cause any ill effects on sexual health and does not lead to any other adverse health consequences. So, you needn't worry about this. So, having masturbated before will not affect your furute marital life.
Many persons have a misconception that masturbation causes sexual and nervous weakness and other health problems. However, this is not true and is just a myth. However, if a person is develops excessive guilt due to this habit, then this can result in
anxiety about sexual performance, which in turn can affect sexual performance. So, I would advise you not to develop any guilt or anxiety about this and stay relaxed and confident.
Wish you all the best.
Regards,
Dr. Jonas Sundarakumar MBBS., DPM., MRCPsych.(U.K.)
Consultant Psychiatrist