Since I don't know who Cris and Joana are exactly, it's really difficult to tell their full story. Maybe they are characters from a local story in a particular region, or they could be two ordinary people with a story known only to those close to them.
One possible story could be that Cris and Joana are childhood friends. They grew up in a small town. Cris was always more adventurous and Joana was the shy and studious one. As they grew older, Cris convinced Joana to go on a trip around the country with him. During the trip, they faced many challenges but also discovered new things about themselves and their friendship grew stronger.
I don't know the exact 'Cris Soto Joana fanfic', but generally in fanfics, there can be themes related to the characters' backstories. For Cris and Joana, perhaps there are themes about their families, their past traumas, and how they heal and grow. Also, if they are in a particular setting like a school or a workplace, themes about competition and cooperation might be present.
Marcus Luttrell is a Navy SEAL. He is the central figure in his own story. He was part of a special operations mission and became the sole survivor of a tragic event during that mission.
I haven't come across 'Cris Soto Joana fanfic' myself. But usually, to find fanfics about specific characters, you can also check out relevant fan communities on social media platforms. Sometimes fans share their works or know where to find them. Maybe start by looking for groups dedicated to the source material that these characters might be from.
Marcus and Dom could be two friends who had a very eventful relationship during their lives. Maybe they were soldiers together, or they grew up in the same neighborhood and had many adventures.
I'm not very familiar with 'el fuego del destino based on a true story' specifically. It could be a movie or a book. Maybe it's about someone's journey full of challenges and how they overcame difficulties in a real - life - inspired scenario.