Create a section in webflow and make its position relative
Create a div and define its size according to the video you want. Place that video inside that div, and make adjustments as you wish to the video, such as auto-play, looping and etc.
a) In the position tab, make it as absolute-fullscreen and give it a Z-Index of 2
Create another div with the same size and give it a black background with 70% opacity.
a) In the position tab, make it as absolute-fullscreen and give it a Z-Index of 3
Create another Div, place your text inside it.
a) Set its position to relative and give it a Z-Index of 4.
That should do the trick. I hope Iβm not missing on anything here.