When I took the planets, the temples gave me a positive resource , and now it is negative.

Will it ever be positive again or not? And if so, how long will it take ?

If you have under 25k points it is positive. Over 25k point it stays negative until you destroy it or you relocate your planet.

If you stop building the bonus % will slowly decrease until you're negative and even farther. Keep building to keep the bonus up.