renault megane 1.5dci not engageing gears

hi all any body help me ive git a renault megane 1.5dci 2006 6speed trouble is i can not engage gears with engine running sometimes it does but not often and then there still also with the engine running i try to put in gear but wont go in full but the car starts to move very slightly ive a new cluch slave cylinder 3000 miles ago and all was fine car goes in every gear when not started cluch feels like its there any help will be great full please help need sorting for work thankyou