Hi! If he is from São Paulo you can also say (with slang): "Meu, sem zoeira, gosto muito de você!" I bet you he'll be impressed! About the pronunciation you can simply put this in google translate to hear, it's not perfect but is good enough. Bye [emoji][emoji]

Eri, you are right: 'eu te quero' might have erotical connotations, while 'eu te amo' sounds too deep and might indicate a serious promise of longstanding, faithful relation. 'Eu gosto muito de você' is usually adequate for something honest and warm, but also free to wait for how else things turn out. The verb here is 'gostar de': 'O que você gosta de fazer no tempo livre?' (What do you like to do in your free time?), 'Eu não gosto de cebola crua' (I don't like raw onions), 'Eu gosto de você' (I like you). As for 'muito', it can mean: a) alot, very much ('Gosto muito de cinema': I like movies alot); b) very ('Esse filme é muito engraçado': This movie is very funny); or c) much, a lot of, many. In the meaning c), it has number and gender inflections: 'muito amor' (much love), 'muita paz' (much peace), 'muitos amigos' (many friends [boys or boys and girls]), 'muitas amigas' (many friends [girls]).

I like you a lot is: gosto muito de ti/você

In Portugal we should say "Gosto muito de ti / si" or if you want to say "I love you" "Amo-te" or formal "Amo-o /a". For say the opposite "Não gosto de ti / si" or "Não te amo" or formal "Não o /a amo".

"I like you a lot" is the same as "Eu gosto muito de você", but that CAN sound a bit unnatural, it will depend on the moment you said it, you can also say something like "i really like you"; "eu realmente gosto de você", or with a bit of a slang in the begging like "man, i like you a lot", well it was not a slang in reality, don't know, btw, it will be like "meu, eu gosto muito de você", of course the intonation and the time you keep every word can give a different vibe to the phrase. Edit: pt-br, don't know if in pt-pt that sounds fine.