First of all, the term 'bad quality' is understood here as low detailing. There are two constituents that influence it in most cases: video quality and output video resolution.
To change the quality and increase it use the slider of "Video quality". You can find it at the "Video" tab of settings or if you click "Output video settings" on the main application panel.
Try to change the output video resolution. We use Full HD resolution by default, but you can increase it if your display supports the higher resolution. You can find this option the same way as we've described above.
Keep in mind that using the max value of both of these constituents gives the biggest file size. We advise using the value of quality equal to 70-80%. It's an optimal value for a good image and file size