There is no big difference between filter and overlay. Usually filter means the internal effects while overlay means external effects.
A transition is designed only for merging the items(videos, pictures) on the video track smoothly, so it should be simple and short.
Based on this prinple, the maximum length of a transition is designed according to the length of the adjacent items(videos, clips), in general the maximum length equals 1/2 of the total length of the two items around it.
You can ajust the length of a transtition by putting the cursor to the edge of it and then the cursor will become a two arrow icon and you can start to ajust it.
If the length of a transition is at a maximum value, then it can't be increased.
To add a watermark to the video, please follow below instructions:
1. Press "Import " button to load the video file and the watermark image to the Media Library.
2. Drag and drop the video file and the watermark image to the video track and PIP track .
3. Then adjust the size of the image by dragging the small circles around the frame. You could also move it to the position where you need.
4. Then change the duration of the watermark image to the same length as the video by dragging the edge of the image file.
To remove the original audio and add a new audio to the video file, please follow below instructions
1. Click Import to load the video and audio files to the Media Library. Also drag and drop the video file onto the video track.
2. Select the video in the timeline, right-click and choose Audio Detach.
3. Then the audio part and the video part will be separated. Select the separated audio file and delete it.
4. Drag the new audio file from the Media Library to the audio track of the timeline. Meanwhile adjust the audio and move it to the place where you want it to be.
To fade in/out at the beginning/end of the video, please follow below steps:
1. Press "Import " button to load the video file to the Media Library.
2. Drag and drop the video file into the video track.
3. Find the Sample colors under Media tab, choose black and drag it at the beginning/end of the video.
4. To change the duration, you just need to put the mouse on the edge of the sample color and when it turns into , please drag it to the length you need. Or you could double click the sample color on timeline and adjust the duration directly.