for what purpose God created you on this earth?

We all have different purposes but all these things pertains to glorifying God, the question is how. I can never know your purpose because it is God's secret to you, He alone could tell you that. We could only know God's plans for us through intimacy with Him. When you are very intimate with God, then ask Him what purpose for you and He will tell you when you are ready.

I think my purpose in this earth is to give care to what gods made like animal, trees, mankind, in short nature

We are all made in the image of God with a purpose to receive His nature and character and to be called one of His childrens. If you are His son you are destined to be with Him in eternal life. While we are still alive , we have to believe in His existence and worship Him in spirit and in truth. To receive Him as our personal savior is our ultimate purpose in life. That is our passport to heaven. We are just temporarily living on this earth. We are bound to be Him in eternal life.