He says i work well when nobody is around and tends to belittle me when others and bosses are around. He intentionally says that things are not urgent (even though they are) so that I get a bad reputation for not finishing projects in time. I am a competent worker but my people skills are very poor. I just do not know what to say, I completely lack diplomacy or tact. I believe i have made the relationship sour by saying things such as *I* have a lot of things to do (accidentally implying that he has less to do) in front of others. Other mistake I have committed with him is that I lightly pointed out the technical mistakes he and his superiors do in work that comes to me.
The job itself is quite new and unfortunately I cannot quit. Please tell me how to fix the relationship with my superior. Please help!