My lover

Today, I finally understand the pain of your lover being other's girlfriend. Sometimes I feel the life is tricky, when you love someone, but she doesn't do the same. Oh, that is life and should be learnt!

I hope this correction helps. In your text you just need to change change:

"being another's girlfriend"

"but she doesn't feel the same"

And here's some other suggestions:

Today I finally understand the pain of your lover having another boyfriend. Life can be tricky when you love someone and she doesn't love you back. Oh, that's life and a lesson to be learnt!

Today I finally understand the pain of loving someone who already has a boyfriend.

Today I finally understand the pain of unreciprocated love. Life can be tricky when you love someone and they don't feel the same. But that's life.            (Un-re-sip-ro-ca-ted)

My Lover

Today, I finally understand* the pain of your lover being another's girlfriend. Sometimes I feel that the life is *tricky; when you love someone, but she doesn't *do the same. Oh, that is life and should* be learnt!

*I have finally understood

*deceptive, deceitful

*reciprocate, respond (likewise), respond in the same way

*we have to learn !