I want to download a replay video of my game. I searched on Google but found nothing. Is there any way to download DotA 2 game video? I mean my own games and not another player's.
You just start the replay and record it yourself with a video recording software.
So after you have setup Fraps or OBS you need to put the "Record" function on a hotkey. Then when you are ingame you press the "Record" hotkey and record the things you want to.
In the end you have your recordings as video files. You can use a video editing software to cut your recordings together and add effects. Just search for a free video editing software. In the free ones you can usually do cutting. If you want better effects you probably need to pay. Adobe Premiere Pro or Sony Vegas are two good options. But there is probably a good free one out there ...
If you don't really want to cut your videos, you need to make a good recording that you want to upload.