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Hello,
I am not sure whether the three sentence makes sense in term of grammar and semantics.
Can you give me a hand with checking them
Thank you for your help.

The idea environmentalists underscore is to make undamaged or undeveloped lands remain their original conditions.

Only by the way I invest most of my time in books do I become a leraned person and perform my job in apple-pie order.

English is like a sea containing infinite knowledge waits for me to pick up, so I have no extra time to accompany and play with my friends.
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Hi kk and Amandine - "in apple pie order" is an idiom, although it's not really used correctly here. It means "very neat and tidy," so you might say "she keeps here desk in apple pie order." It would not be used to describe doing a job well, and it does not mean that the job literally involves apple pie. How about this for the second sentence:

"Only by investing most of my time in books can I become an educated person able to do my job well."
Comments  
Hi kk

The idea environmentalists underscore is to make undamaged or undeveloped lands remain in their original conditions.

Only by the way I invest most of my time in books do I become a learning person able to perform in my job which consists in ordering apple-pie .
But I think it's still kind of long..

English is like a sea containing infinite knowledge waiting for me to pick it up, so I have no extra time to accompany and play with my friends.
 khoff's reply was promoted to an answer.