So we just have to work out from context whether it is 'yours' or 'theirs' when 'deres' appears?
This is different from English. In Norwegian "deres" is plural, so it refers to a group of people. One person, singular, is specified using "din" or "dine". (If someone wanted to be very archaic, "Deres" could be used when referring to one person.)
Yes, just like how in English, you have to work out from context if you mean one or multiple people with 'you'.
That would be another viable option, with a slightly different connotation.
"De liker ikke dem" = "They don't like them" ...but someone else. The focus is on the object.
"De liker dem ikke" = "They don't like them" ...focus is on either the verb itself or the negation.
Based on Deliciae's response, it sounds like you wouldn't say, "They like not them" unless that's only the beginning of a sentence that would be followed by further clarification. For example, "They like not them, but us." When it's just a complete sentence by itself, it makes more sense to say, "They like them not." What comes to mind for me is the phrase, "He loves me, he loves me not."
not being funny but i still get confused when to put ikke after the verb or at the end of the sentence
How do i say "Your bosses don't like them." ? Your as a plural meaning. So that the short form for example "Your bosses don't like the suppliers" the first sentence is.