marcello

How do i write in a birthday card...

Wishing you a very happy birthday. You have been more than a good friend to me. Thanks for all the fun times. Good luck to my little friend.
Now we can be just good friends.

Hebe

Hi Marcello, here is my translation attemp, I hope it helps !!!

Deseándote un feliz cumpleaños. Eres para mí más que una buena amiga. Gracias por todos los gratos momentos. Le deseo buena suerte a mi amiguita. Ahora podemos ser simplemente buenos amigos

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"To him whose elastic and vigorous thought keeps pace with the sun, the day is a perpetual morning". Henry David Thrreau"

marcello

Thankyou so much for your help. Just one thing i am female writing to a male so how do i say good luck to my little friend ( ie to a male )

Hebe

Buena suerte a mi pequeño amigo

__________________
"To him whose elastic and vigorous thought keeps pace with the sun, the day is a perpetual morning". Henry David Thrreau"

Ichux

I'd say:

Te deseo un muy feliz cumpleaños.
Has sido más que un buen amigo para mí. Gracias por toda la diversión. Buena Suerte a mi amiguito. Ahora podemos ser solamente buenos amigos.