As for the freezing you can try wiping the cashe partition [https://www.youtube.com/watch?v=u32sA0E5pWM|this video] shows how on most samsung tabs If this brings no joy you may need to do a complete factory reset. this will cause a lose of all data so remember to back up what you want off the tab before preforming the factory reset . As for the oil stain on the screen could you please post a picture so we can see what you mean This [guide|21499|link] shows how to add a photo to this question . Was the tablet dropped or has it got wet . Knowing this can also help in fixing it. Hope this helps