from the very beggining???
it is not possible to do so in 3 sentences--besides i dont know quite a bit of it. this is what i know. others feel free to add or correct.
kashish gets a job at R&G. sujal (old) is her boss-they dont get along but eventually they fall in love. Sujal's best friend is Piyush. Piyush too is in love with kashish. Circumstances arise where kash marries piyush and then eventually falls in love with him. (although keep in mind she has never truly forgotten sujal!!!). Sujal goes crazy (kind of) and turns against his best friend and love. Then piyush dies. kash and others blame sujal. Kash is pregnant at that time. Sujal proposes to kash on piyush's tervi. She says no obviously but then ends up marrying sujal to punish him for all the hurt he gave her when she was married. Sujal is a very nice guy because he truly will do anything for his love. Kash plays with him, and haunts him by bringing up piyush all the time---but slowly slowly she starts to feel for him again. In the meantime, sujal goes to jail for piyush's 'accident'. Then kash finds out the truth that sujal was in fact not respeonsible for piyush's death. Then kash finally admits to herself that she is kidding herself when she wants to hurt sujal becasue she ends up hurting herself in the process. She quits her revenge plan and everything is okay. Then something happens and they get into a fight and she leaves and goes back home. They patch up soon and sujal on his way to get her, gets into an accident and dies!!!!!! but body is never found!!!!!!
Soon after, somebody (tusshar) comes into storyline and has an operation. He has disfigured face and no memory of his past. He is sujal. tusshar beleives that he is in love with kash and she is quite attracted to him as well.
Dah dah dah dah dah......they get engaged. Wedding is soon to happen.
Now people find out that swayam (villain) was responsible for sujal's death. he is put on trial but he figures out that tusshar is in fact sujal. He informs everybody that sujal is alive. Nothing else.
TK Wedding is cancelled. Now everybody is in search of sujal. This leads kashish to delhi hospital. Basically dead ends. Meanwhile charu (kash's sis) beleives she is in love with tusshar. Kash wants tusshar to marry her. Swayam makes a deal with tusshar that if tusshar will marry charu (his friend) then he will tell everybody where sujal is. Wedding happens and i think you know the rest.
hope this helps. welcome to the board.