Basics

in Sequencer Add Movie or Drag and drop/

Audio track is green, video track is mauve.

You need to select the length of the video by adding Start and End keyframes in the Sequencer panel.

Video cutting

Use k to cut the video at the cursor point/

Trim video,

RClick on one end, then G to move.

Overlay video

H hide video

Only video on top are visible.

Use Shift+S to adjust the head towards the key 0 or the last.

Effect Strips

You can add effect strip,

e.g you add Transfeorm, modify the uniform scale (thus you can make a tiny video on top of another)

You can use a blend mode in Edit Strip.

You can add multiple strips nested on top of another.

Transitions

First overlap 2 video chunks on 2 different tracks.

Select the head of the first which is on top and select Transparency 0.5

Edit Strip > Opacity

The select the rear end of the video which is on bottom and select Transparency 1.0

Hit I to create a keyframe, if you want to have a modifiying strarting point.

Adjust Speed

Rclick to select the rear end of a video Now drag the end back and forth to adjust the speed.

Adjust Text

Add text, you do adjustments.

Rendering

In Scene tab, adjust 1920x1080, each clip has its original dimension listed in Edit Strip side panel.

Percentage: 30% of the original res just to create test videoclips.

Frame Rates: pick your choice, 25

File format: ffmpeg video

Encoding: MPEG4

Sound: MP3