Actress Karishma Tanna, who is gearing up for the release of her second Hindi film "Sanju", says her co-star Ranbir Kapoor is amazing to work with and is a complete brat.Asked how would she describe Ranbir, Karishma told IANS here: "He is amazing, a thorough professional and a brat. He's a lot of fun on the set. He has very good humour, talks well and a lovely guy to work with.""Sanju" is directed by Rajkumar Hirani and also stars Sonam Kapoor, Vicky Kaushal and Anushka Sharma. The film is slated to release on June 29.This is not the first time Karishma, who is all set to feature in Star Plus's "Qayamat Ki Raat", will be seen on the silver screen. She was also a part of the third instalment of the "Masti" franchise.Karishma is not in a rush to sign films."I had been offered a lot of films also but if the content is not good then I would not want to do it...," she said.