Hello. To delete the videos you have seen in the collection, you can first click on mine, then enter the history, and then click on the collection. You can click on the three points in the upper right corner (if any), and then there will be deletion. Click Delete, and then there will be selection all. You can choose to select all or delete what you want to delete.

But there may not be three dots in the upper right corner, because I can't remember them. If not, you can press and hold the information or video you want to delete, and then the words Delete and Select All will appear. You can choose to select all or delete what you want to delete.

Please forgive me for being wrong. I hope my answer is helpful to you.