I believe I see two mistakes, and SraJMcGin may find others.
The proper expression for "more than" is más que, not más de.
"va a sera" in the last sentence should be "voy a ser", since (I presume) you are the subject of the verb, and the infinitive should follow "voy a"
First of all the screen name "Anonymous" does not tell me if you are male or female! I need to know that to correct the first sentence.
Soy una bueno candidato = un buen candidato OR una buena candidata = all adjectives have the same number (singular/plural) and gender (masculine/feminine) as the noun(s) modified
dedicada, = this adjective tells me you must be feminine, so I'll correct everything that way
He estado nadando para más de cinco años. this is a literal translation (word-for-word) and that does not work because there is an idiom to say that = Hace más de cinco años que nado. = I have been swimming for more than 5 years.
Soy entrenado para ser un salvavida. = I would restate that using the verb "to train/be trained" = Me he entrenado para ser salvavidas. (with ser, there is no "un/una" when noun is unmodified. (This noun is salvavidas = singular or plural because you save more than 1 life!)
I like to be outdoors, = too literal = Me gusta estar afuera (OR "al aire libre")
alrededor de piscina (it would be "alrededor de la piscina" BUT there is no way you can be "around" the pool, like a hose could be. Try "cerca de una piscina"...
I am going to be a responsible lifeguard. = Voy a ser una salvavidas responsable.
NOTE: Oh dear, I found more than 2! Don't feel bad; if you wrote it in English first and then tried to translate, that would explain the errors. Always try to write just in Spanish first, if you can, using the structures and vocabulary you have mastered. Ordinarily it is "más que" but you were correct in that it is "más de" before a number.