@ahmmedessa by purely doing the thing you are a competitor. As in you are competing at something. To be competitive you would have a chance of winning.
Let's say San Marino are playing Germany at football. They are not going to win as Germany are so much better. So they are NOT competitive. However they are still participating so they are a competitor.
'Competitor San Marino lost the game 10-0' 'A competitive Spain team narrowly lost 2-1'
Note - there are various contexts other than this you can use these words. But I feel that is the main distinction.