Ah thank you. That solved it. I just wonder. I re-created the top again, but it resulted in the same problems. Which step is actually wrong in my process:
Goto Object mode >> SHIFT+A , add cylinder >> R, Y, 90 , ENTER >> S, X, 1.8, ENTER >> go into edit mode >> choose vertex mode >>
delete the lower half of the vertices >> create horizontal faces with F (addon mentioned in video), last face add the other top 3 faces and create a face with 5 vertices)
All faces look ok. (normal lines all point out from all faces). Double check: enable blue/red colors, all outisde colors blue. So ok.
Press E (extrude from faces), right click to chancel (you mentioned, press ENTER) . The extrude does not work normally as in your video. CTRL+Z back to before I pressed E, then try again.
Right in above step it goes bad again. But after a CTRL+Z several times, stop CTRL+Z right after undo the E action, and repeat from extrude again, it worked normally.
Really strange.
But somehow it worked now. I am repeating the same steps to re-create the issue, I saw the issue, but right after re-doing and trying to get the error again, it worked now. I am baffled. Now I tried for 3 times and no problems what so ever. I do not know how and what went wrong. Really trying to get the same mistake back. Cannot.
But, thank you, it is working now. Really strange.
