You can say "Tengo cinco años".
The word we'll is a contraction for the prounoun 'we' and the verb (or auxiliary verb) 'will'. If the speaker and another person are both going to be five years old, then it is correct to say: We'll be five years old. (We will both be five years old.) If the speaker is referring to them self only or any other persons or things, it is correct to say: I will be five years old. You will be five years old. He will be five years old. She will be five years old. It will be five years old. They will be five years old.
The expression to say how old you are or a material object is in Spanish is "tener ____ años".If you literally want to translate "years old" into Spanish, this would be "años de vejez", but this is nonsense to any Spanish speaker.
i am 41 years old
cien años
años de edad
Tengo diezisiete anos.
Tienes quince años.
Tienes deiz años.
Tiene veinticinco años.
Mis amigos tienen doce años. This is literally "My friends have 12 years", but is normally translated as "My friends are 12 years old."
I am 55 years old: J'ai cinquante-cinq ans.
i would say it about right.normal