Ok, here is the sentence broken down:
I will always be your evil queen.
I will be = verb ero (first person future singular of esse "to be"), you can put ego "I" but it is understood by the conjugation of the verb.
always = adverb semper.
your (singular) = adjective tuus/tua/tuum, must agree in gender with its noun, regina.
evil = adjective malus/mala/malum, must agree in gender with its noun, regina.
queen = feminine, 1st conjugation, nominative noun regina.
It's perfectly normal to get stuck, Latin is a huge investment and will demand a great deal of your time if you want to become proficient at it. There is also no particular order that most of those words had to go in, I just chose the one that seemed simplest.
flebile nescio quid queritur lyra, flebile lingua murmurat exanimis, respondent flebile ripae