では can mean "at~, in~, in ~~ respect, as far as~~ (is concerned/I know), judging from~~, regarding~~, as for~~", (so it's like ~について言えば/~に関しては/~という点からいえば/~という点から見れば) as well as "Then, OK then, Bye" (when used by itself or at the beginning of a sentence) and "I suppose~" (when used at the end of a sentence), etc. し is a conjunctive particle (接続助詞), or a parallel particle (並立助詞); "~and, besides, ~~and moreover, plus, ~~too." It also can be used to express a reason, like "Because~/ As~". 一緒に過ごせる時間の多さでは would literally mean: Regarding the length of the time we (=you and I) can spend together, / Judging from the length of the time we (=you and I) can spend together, / When it comes to how long we can be together, 勝てないし I can't beat (or defeat/overcome/excel/surpass) her (and besides~~) or, (Because) I can't beat her (regarding~~.) So the line is saying "I can't spend more time with you than she spends with you (and moreover~~. /and besides ~~.)"/ "Because she spends more time than I can spend with you." 名前だってちゃんと呼んでもらえてなくて And (besides,) you don't (even) call my name properly. / And (what's more,) you don't even call me by my (supposedly "first") name. --'Cause we Japanese normally don't call one's (normally of the opposite sex) first name till you become close friends or gf/bf.