Jesse and Celine are in their early 40s, now married and on a summer vacation ion a Greek island.

After meeting Celine, Jesse has divorced his ex-wife and now livinglives in France with herCeline.

The couple hasve two twin daughters and from time to time they takes care of Jesse's son with his ex-wife.

without the "they" it sounds like you're talking about an specific person instead of a couple :)

While happy with his life, Jesse feels like he should spend more time with his son, and this triggers an argument between him and Celine.

Besides the issueOn top of that, Celine feels like she has to give up her life taking care of her husband and daughters all the time(/ daily).

Besides the issue doesn't really make sense, but if you replace it with "on top of that" you're saying that there's something more happening besides the fights between Jesse and Celine :)

In a hotel booked by their mutual friend, where they are supposed to spend a romantic night, they gets into an argument, which getcauses Celine to say that she doesn't love Jesse anymore.

The letter says that they are still happily married 40 years later and says at the end that one of the best nights she's ever spent was on the Greek Island, where they are now in.

Celine is initially hesitant to reconcile but gives in when Jesse says that he is trying his best to keep(?) his true lovestay together, and that they are not living in a fairy tale.

Your sentence was fine, although "keep his true love" sounds poetic but not as natural :)

4. Although the trilogy wasfilms were low-budget movies, the locations and romantic yet realistic dialogue of the characters gave me a lot to think about.

I thought about what love is and if there iswe really have a soulmate.

by saying "if there is really a soulmate" gives off the nuance that there's only one soulmate in the entire world :) you can also say " if everyone really has a soulmate. "

Love seems perfect at first, but couples run into various problems as they spend long time together.

As couples gets older, your partner may not look as attractive or as perfect as they used to look/be.

It was because, deep inside, they had trust fored each other, that they are still lovingin love with each other and are willing to reconcile(?) to bestay together.

I hope I will be able to meet someone with whom we canthat I can devote myself to/ that can be as devoted to each ome as I am to ther.m

whom sounds extremely formal :)

Jesse and Celine are in their early 40s, now married and on a summer vacation ion a Greek island.

After meeting Celine, Jesse has divorced his ex-wife and is now living in France with her.

You might want to say who they are living in France with because it seems you are saying they live in France with they’re ex wife.

The couple hasve two twin daughters and from time to time they takes care of Jesse's son with his ex-wife.

While happy with his life, Jesse feels like he should spend more time with his son, and this triggers arguments between him and Celine.

Besides the issue, Celine feels like she has to give up her life takingo take care of her husband and daughters all the time(/ daily).

The first part doesn’t quite make sense

In a hotel, booked by their mutual friend, where they are supposed to spend a romantic night, they getsot into an argument, which getsen Celine to says that she doesn't love Jesse anymore.

The letter says that they are still happily married 40 years later and says at the end that one of the best nights she's ever spent was on the Greek Island, where they are now in.

Celine is initially hesitant to reconcile but gives in when Jesse says that he is trying his best to keep(?) his true love, and that they are not living in a fairy tale.

‘To keep his true love’ does make sense but something like ‘to stay together’ may be more natural

4. Although the trilogy wasfilms were low-budget movies, the locations and romantic yet realistic dialogue of the characters gave me a lot to think about.

I thought about what love is and if there iswe really have a soulmate.

Love seems perfect at first, but couples run into various problems as they spend a long time together.

As couples gets older, your partner may not look as attractive or perfect. as they used to look.

It was because, deep inside, they had trust fored each other, that; they are still lovinge each other and are willing to reconcile(?) to bestay together.

I hope I will be able to meet someone with whom weI can devote to each othermyself to.