it's not always the player having the best cards who win, but the one who puts the right cards on every turns he has.It's not always the one having the best cards who wins, but the one who throws the right card on the table in every turn.
I think i got an example that fit this well.
.... this sentence does not serve any purpose. Better you leave it out.
Once, i had two seniors in my high school which are brilliant, well behaved, and both of them joined chemistry olympiad class.
.... this sentence needs imporvement;There were two brilliant and well mannered seniors in my high school who joined the Chemistry Olympiad class with me.
One of them decided to focus on the olympiad things in the second year and focus on the other subjects on the first year as it should be but one of them took the risk on the other subjects by focusing on the olympiad things since the first year.
This sentence is too very long and sounds confusing. Break it up to contain one idea per sentence.