Names are spelled the same way, no matter what country you're in, and you should try to pronounce the name the same way the person pronounces his own name.
However, if you're naming a child in Sweden, then you would probably spell it Jonatan, if you want it to be pronounced the Swedish way.
Jonatan is pronounced kind of like you-na-tan, where the a-sound is the same vowel sound as in the word Are.
"Me llamo Johnathan Walker", or "Mi nombre es Johnathan Walker".
¿Cómo están tú y Johnathan?
And is "och" in swedish.
På svenska
"King" in Swedish is "kung".
Suedoise is French for Swedish.
"Goal" in Swedish is "mål".
Equality is "jämlikhet" in Swedish.
Episode is episod in Swedish.
Small is liten in Swedish.
29 is tjugonio in Swedish.
Fire is eld in Swedish.