Maybe your feeling is not “jealousy”, it is “admireation” or “envy”.

I often envy some relationships in anime because it is perfect in a fictional world becauseand the hero and the heroine always break obstacles and end up together.

You used the word “because” twice in the same sentence so I tried to make it sound a bit more natural.

It makes the relationships and loves more valuable like the gold does not fear fire.

You should believe yourself whether you would like to think something negative or not is goodfine, you are nicer more than you think.

I remember I used to get into onegot into a crazy relationship crazy.once.

I fell in love with a girl and she often feelslt “jealous” because I have some heterosexual friends and she feelslt I geot in touch with them too closely.

However, I was never mad because of her unexcused propaganda and criticizesm because she loved me and doidn’t want to madke me mad.

You should love yourself and have more concretion to other positive things.

I don’t think you use the word “concretion” correctly here and I never see the word so just letting you know. Maybe say something like “and open yourself to other positive things”.

For example, you can try to find a partner and enjoy a relationship in love.

I’m not sure why this sounds wrong to me. I think “and enjoy a romantic relationship” would sound better

You are not wrong.

This is a little unusual. Are there two people riding the story? Who is saying you are not wrong?

Maybe your feeling is not “jealous”, it is “admire” or “envy”.

Maybe you are not feeling jealous, but instead you admire the fictional character or you aspire to be like the character.

I often envy some relationships in anime because it is perfect in a fictional world because the hero and the heroine always break obstacles and end up together.

I often envy relationships in anime because they are perfect in the fictional world. The hero and the heroine always overcome obstacles and end up together.

It makes the relationships and loves more valuable like the gold does not fear fire.

I do not know what you were trying to say here. Gold does not fear fire is not an expression we would use in the English language.

This feeling is human nature.

This is a correct sentence but it doesn’t really mean much. Perhaps you could say “The desire to love and be loved his human nature.”

You should believe yourself whether you would like to think something negative or not is good, you are nicer more than you think.

This doesn’t make much sense. Are you trying to say you should believe in yourself weather something is positive or negative? The last part of the sentence Should either be “you are nicer than you think” or “you are often nicer than you think.”

I remember I used to get into one relationship crazy.

I remember I used to get into crazy relationships.

I fell in love with a girl and she often feels “jealous” because I have some heterosexual friends and she feels I get in touch with them too closely.

I fell in love with a girl and she is often jealous because I have other female friend and she feels I am too close to them.

However, I was never mad because of her unexcuse proganda and criticize because she loved me and don’t want to made me mad.

Unexcuse is not a word.
However I was never mad because of her excuses and criticism. She loved me and I did not want to make her mad.

You should love yourself and have more concretion to other positive things.

You should love yourselves and have more of a connection to other positive things.