How can i show off my strenghts without sounding arrogant?

Showing that you are aware of your strenghts is essential. In order to avoid giving the impression of bragging, you should support each statement you make about your strenghts (or at least the most remarkable ones) by providing an example that objectively proves it is true. E.g. if you state that your communication and teamwork skills are your best strenghts, you could support this by saying that, for instance, during group-projects you always interacted with all your group-mates in a respectful and costructive way in order to create the best working enviroment to produce the best result you possibly could. If you also have non school-related experiences in which you made use of one of your strenghts, make sure to include them: it shows that you are versatile enough to recognize how your strenght can be applied in everyday life and that you actually know how to do it (it is not always implied).