I often spend my free time in solitude and in staring at the bright blue sky.

I also like to read books on human intelligence and psychology as it helps me understand human nature, this way I learn how to socialize with others efficiently.

I often spend my free time in solitude and in, staring at the bright blue sky.

I think there are a lot of ways you could say this sentence. It sounds very literary here.

I also like to read books on human intelligence and psychology, as ithey helps me understand human nature, t. This way, I learn how to socialize with others efficiently.

In my free time I like to reflect on the purpose of life.

You can absolutely say "purpose of life" but the phrase "meaning of life" is very common in English and means the same thing, so maybe use that phrase instead. Both are correct English and easily understandable, though.

I often spend my free time in solitudalone and in staring at the bright blue sky.

"In solitude" sounds very formal.

I also like to read books on human intelligence and psychology as it helps me understand human nature, t. This way I can learn how to socialize with others efficiently.

I love to think about ways to improve myself.

You could also say "I love to think about ways of improving myself.", which would sound a bit more natural for a native.

I also like to read books on human intelligence and psychology as it helps me understand human nature, t. This way I learn how to socialize with others efficiently.

I would also be natural here to say "I also like reading books about..."