"I do not want you to suffer."
Translation:Jag vill inte att du ska lida.
”Ska” forms the future tense so it’s literally ”I don’t want that you will suffer” which is how we express it in Swedish.
I want to add that this only works with the ”modal” future with ska, not with the ”predictive” future with kommer att.
I said "Jag vill inte att du lida" but it says it should be "lider" - why? Isn't infinitive?
You can say either Jag vill inte att du ska lida or Jag vill inte att du lider.
The reason your version doesn't work is that lida is in the infinitive, so it doesn't work on its own. With a verb in the infinitive, you always need an auxiliary that shows time.
I am also confused, in this other thread it had to be the infinitive for ...min pappa gråta. I don't understand the differences in grammar in the 2 sentences that makes 'gråta' have to be in the infinitive and "jag vill inte att du lider" cannot be in the infinitive. https://www.duolingo.com/comment/6084258
I can't remember the grammatical term for it at the moment, but it's the same in English really. For instance you say I saw him cry where cry is the infinitive, not the present tense. It's less clear in English but you can see it in the third person because it would be he cries if you said it like I can see that he cries.
So when a pronoun in the object form needs a verb, that verb is in the infinitive in both languages. Jag såg honom gråta 'I saw him cry'.
In the Swedish sentence here though, we don't have an object, we have a new clause instead, where it's du, not dig, so that du is a subject. So we're saying literally either 'I don't want that you will suffer' or 'I don't want that you suffer'.
We cannot have dig as an object of the verb vill because vill in Swedish doesn't work the same way as in English. As I'm sure you know, it's vill ha for wanting things (nouns), and vill is only used with verbs. So the whole construction want X to is always vill att X [ska + infinitive/present] in Swedish.
Sorry this got a bit long but sometimes writing short answers takes so much more time! :)