Check this sentence please? Tack!
Hej jag ar en pojke. Alex ar en flicka. Nej. Han ar en Kvinna. inte bara en kvinna, han ar en spindel. Tack mycket for laser det.
First of all, it's very important to distinguish between a and ä and å in Swedish as these are separate letters and in some situations crucial to make yourself understood. So it's "är" not "ar". Also, practise those pronouns, you used "han" here instead of "hon" (han is the male pronoun and because you're telling us Alex is a woman, you want to use hon, the female pronoun). Last sentence is a bit off, I'm assuming you want to say "thanks for reading", which to be honest, I think is a bit awkward to translate into Swedish, but I'd personally say something along the lines of "tack för att ni läste det här" (or actually, honestly, "tack för att ni tog er tid att läsa det här", which is a slightly different sentence if you translate it word by word, but better conveys the meaning of the English sentence imo), which contains some grammar that is probably beyond your level right now, but if you have any questions, feel free to ask -- Swedish is my first language.
Like Megaost says, accent marks are important in Swedish; you can't write without them because they change the pronunciation, and sometimes, the meaning. Likewise, you don't capitalize nouns like "kvinna" in Swedish. If I were to translate this, I would probably write:
"Hej, jag är en pojke. Alex är en flicka. Nej. Hon är en kvinna. Inte bara en kvinna, men en spindel. Tack så mycket för att du läste det här."
Remember that han is he in Swedish, and hon is she. You seemed to have mixed your pronouns. The way to say Thanks for (doing something) in Swedish is Tack för att du/ni (verb), hence the last translation, but I agree with Megaost that Tack för att ni tog er tid att läsa det här might sound better. More literally it translates to Thanks for taking the time to read this.