Level design for Urban Terror is one of the most problematical areas for map makers. While it's relatively easy to construct and decorate your maps, it's fiendishly difficult to create an addictive level that will appeal to a significant number of player.
Reading articles will help you learn the basic concepts and "buzz words" of layout design but most tutorials on the subject discuss layouts for games which include rocket launchers or less mobile games.
Urban Terror is different. Urban Terror maps must cater for ground based players but also accommodate players who prefer to take advantage of the unique game dynamics.
Drawing a 2d layout sketch may not be of much use, Urban Terror is played very much in 3d. Designing choke points which seem perfectly reasonable to a ground based game may not have considered players who are capable of wall jumping, circle jumping and scaling the unsaleable.
New methods of level design need to be explored.