rendering a film is quite resource intensive. it would be great if kdenlive could offer basic operations like cutting out a couple of minutes without rendering, like avidemux-2.6 can do.
Asked many times, same answer: Kdenlive is a non-linear video editor. MLT is its engine. Ask the MLT developers to support non-recoding cutting. In the meantime you may want to try ffmpeg which can do such cuts, but as any other video software such cuts are only possible on certain frame types and not in general. So, your cuts won't be exact anyway. For simple cutting, MLT on MP4 footage is actually faster than realtime playing on fast systems.
As Wegwerf said, Kdenlive is a NLE what you are looking for is a program like Avidemux. Please close this report. Cheers