The issue is that the Spanish sentence contains two verbs, but you're trying to use the noun "pay". In English, if you want to connect two non-modal* verbs, you usually put a "to" in between (in some cases you can also use the gerund of the second verb):
- I love to watch. - I love watching.
- He needs to calm down.
- They tried to write. - They tried writing.
In Spanish you most often just put the verbs right after each other. The first verb is conjugated in that case, and the second stays infinitive:
- Amo mirar.
- Él necesita calmarse.
- Intentaron escribir.
* Modal verbs are auxiliary verbs that modify the meaning of the main verb, like "can", "must", "will", "shall".
No. This is informational, possible beseeching or insisting, "I need to pay". As opposed to "Me gustaría pagar" -- i would like to pay; "Si pudiera pagar, por favor" -- If i may pay, please; "Me gustaría la cuenta, por favor -- i would like the bill, please; "La cuenta, por favor" -- the check, please.
The letter 'y' can be pronounced differently in different dialects. In most of the Spanish-speaking world it's pronounced like the English 'y' (as in "yes"), but if you go to the Argentine/Uruguay region, it can sound more like "jo" (with a softer 'j' sound, like the 's' in "leisure"), or even "sho".
Yoink, what exactly are you asking about? Are you wondering why the 'c' and the 's' make the same sound? They do that in most dialects, but in a more original Spanish, one that is spoken in most of Spain, 'c' (in front of 'e' and 'i') and 's' do make different sounds. The letter 's' still sounds like a normal [s], but the 'c' makes a [θ] sound, the same sound an English 'th' makes in a word like "thunder".
So necesito is spelt that way because it's "supposed to" sound like [neθe'sito], and that exact pronunciation is realised with those exact letters.
Amelia, there are a lot of forms of that verb. Spanish verbs conjugate for person, tense, aspect and mood, so Spanish verbs change their shape depending on who does it, when they do it, and depending on some other circumstances. All in all, each verb can take about 40 to 50 forms, but they mostly follow regular patterns, so it's not too hard to learn.
For the Present tense, the conjugation of the verb necesitar ("to need") looks like this:
- yo necesito - I need
- tú necesitas - you need (singular, informal "you")
- usted necesita - you need (singular, formal "you")
- él/ella necesita - he/she needs
- nosotros/as necesitamos - we need
- ustedes necesitan - you need (plural "you")
- ellos/ellas necesitan - they need