green screen issues

I am completely new to video editing an am trying to use Fusion to layer a photo over green screen footage. I am using a new Leveno laptop with 16GB, running on a Rysen 5 and running Windows. If it matters I am also using Bitdefender anti virus. I have installed Davinci Resolve 17 and have watched and read through several tutorials on how to use Fusion to layer my mp4 green screen footage with my jpg. file. Two things happen when I try and do this either I upload the video first, key it and then go back to the editor and upload my jpg file. At this point my jpg shows up as my green screen footage with the proper file name underneath. Now if I upload both my video and my photo, add the video to the editor and then key it everything is fine until I go to add the photo, at this point it flashes either just my video or my video and the photo. I have no clue what is going on and I have tried this over and over again with the same results. On top of this at times my video with just be a black screen.

Some screen shot of the fusion node tree and/or view of the editor would be useful to try and see what's going on.

With DVR17 and given you're just beginning, I would actually not use fusion at all, but just use the "media" and "edit" page.

(1) In the "media" page, select both your image and video clip from the "Media Storage" and drag them to the "Media pool" (lower part of the screen).

(2) Go to the "edit" page.
(3) Drag your image on the first video track "Video 1"
(4) Drag your video clip on the second video track above that "Video 2"
(5) Drag the right edge of the image "clip" (on Video 1) to match the length of your video clip (so that the image lasts as long as the whole video)
(6) In the effects library go find Open Fx / Filters / Resolve FX Key and then drag either the 3D keyer or HSL Keyer onto your video.
(7) In the inspector, go to "effects" and use the little color pick tool to draw a short line onto your footage somewhere there is the green screen visible to pick up the right color to key out.
(8) Play with the other params until you achieve a key you're happy about.,