Actually there are plenty of expressions, and they could be expressed either by a sentence or a simple word 1) i miss u so much! - افتقدك كثيرا - اشتقت اليك - اتوق إلى رؤيتك - اتوق إليك - وحشتني موت (This one is colloquial and funny by the way) 2) i love you so much ! - احبك كثيرا - اهواك - متيم بك - مغرم بك 3） i need you very much! ( i very need you) ! - انا بحاجة إليك - احتاجك بشدة - لا استطيع العيش بدونك - حياتي جحيم من دونك (also colloquial and funny) There are plenty and with some creativity, you will be able to make up hundreds of expressions. You can use flash cards for greetings as well if you search them in google, good luck

Depending on the asker ( feminine or masculine ) (m/f) = masculine / feminine ready ? let's learn : 1) i miss so much! اشتقت كثيراً / أشتاق كثيرا maybe you are refering to : i miss you so much اشتقتُ اليك كثيراً : ichta9too ilayka/ilayki (m/f) kethiren . ( said by both m/f) 2) i love you so much أنا أحبك كثيراً : ana oohibbooka/oohibbooki (m/f) kethiren . ( said by both m/f) 3） i need you very much! ( i very need you) ! أحتاج اليكَ بشدة　: ahtejoo ilayka/ilayki (m/f) bichidda . ( said by both m/f) Hope it helps :D

1. I miss you so much أنا أشتاق إليك جدا 2. أنا أحبك جدا I love you so much 3. أنا أحتاج إليك كثيرا I need you very much " I very need you" is not correct!