I doubt if complement and cover are good verbs for strength and weakness respectively in the following context.

I learned how to complement my teammates’ strength and cover their weaknesses to achieve a unique goal.

Moreover, I wonder if ther word how is good there.

I think cover weakness has negetive conotation meaning hiding or sth like that.

I want to say that people who are in the same group can support eachother by helping one another to boost their strong points and remove their weakness.

I would be grateful if you would let me know if you can think of other ways to convey this concept.
I learned how to complement my teammates' strengths and offset their weaknesses to achieve our goals.

You can reinstate 'unique goal' if the broader context is speaking of a single, unusual project.
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is it correct to put it like this.

I learned how we should complement eachother's strengths and offset our weaknesses to achieve our goals.

Thanks again
No, that does not carry the meaning you want.