I did not have any artificial circumcision. My age is 23. The skin streches back but not fully like it should form a mushroom structure at the top?

It's your choice. About 10% of men have a significant problem because the foreskin will not retract, and many more have some restriction. It is your choice whether to be circumcised. It is easier to keep clean / avoid some infections, the risk of gangrene from a foreskin trapped backwards is eliminated, many women prefer it, and some men oppose circumcision of children on grounds of autonomy.
Phimosis. Your foreskin, as an adult, should retract easily and completely. Penis can not be easily cleaned if not fully retractile and sex can not be as much pleasure as it should. Risks of a tight foreskin are nicely listed by dr. Friedlander. Circumcision is not "artificial", it is the intentional removal of the foreskin. Majority of males do not require circumcision, but approx. 105 of uncirc'd males do.