As Turkish illustrated, a lot of the occurences you'll see with لك ,بك, etc are in fixed expressions (so translating phrases literally using the preposition's most common meaning won't always make sense. The phrase has to be memorized as is). Furthermore, prepositions (ie. في, ب,ل, etc.) are never consistent in meaning. What means "in", "at", "with" in one collocation - or group of words patterned together - may mean "on" "to" "for" in another. To further illustrate this in very basic terms: لك could mean for you, to you, "have/possession", association, etc: .عندي هدية لك - I have a gift for you. ...قال لك - He said to you... هل لديك إخوة أو أخوات؟ - Do you have any brothers or sisters? ...المعجم المفضل لي - My favorite dictionary is... ب can also allude to association, "with", "in", etc: .هذه المجموعة الخاصة بك - This group is yours (literally: particular for you). .لا تتردد في الإتصال بي - Don't hesitate to contact me. (Here, as you can see, ب doesn't mean "for", "in", "with", "at" or anything like that. It's just an fixed part of the verb followed by an attached pronoun.) .يبدأ بك - It starts with you. While you can think of these prepositions as having specific meanings, it'd be best to also consider them variables a part of phrases rather than the pronoun attached to them.

shukran laka ahlan bika marhaban bika qultu laka

*can't say, in the first line i meant you can't say it in one word in English.

"بك" has two meaning in Arabic, the first one is "you", and you can say in one word in English by the way but you get it from the context, it simply means that you're referring to someone you're talking to specially in a question for ex. ماذا بك؟ in Arabic means what's wrong with you? or are you okay? depending on the situation itself, "بك" here means "you" and by the way this word is very uncommon during the daily speech of most of Arabic speakers, and it only used in formal situations. also "بك" is an Ottoman tittle for chieftains, in English "Bey" and it was very common in Egypt during the royal era but somehow many people keep on using it till now specially in Egypt & Syria and Lebanon but they pronounce it "beeh". "لك" means "for you" for ex. عندى اخبار جيدة لك which means I've some good news for you and sometimes it refers to possession ex. هل لك زوجة؟ which means have you got a wife? and it also used in formal situations only. I hope that was useful Rajullah.