Hi, I’m brand spaning new to Blender. Started doing Andrew’s tutorial series, how to model a donut.
I am at the end of part 5: https://www.youtube.com/watch?v=6OTX3ZdYvEA
and I noticed a big hole on the back of my donut. It is missing vertices, edge lines and of course faces.
Looking online I find the typical “press F, press J, try alt F” tips and tricks. But nothing really works. At least not without creating very deformed geometry.
So, any help would be awesome.
You have many edges that are missing edges that is why it’s happening. As you are new, I think that the best way is to recreate the icing. That would also give you practice.
you could delete all these vertices and make several grid fill to fill the gap
I guess I’ll go back and remake it. Damn it, I was hoping for a simple solution. A bit like with Sketchup and just draw some lines.
Thanks for the replies 
again, it must be easy to fill with grid fill, give a try
Not easy for this noob haha
Thankfully I did save a copy of icing. So I’m redoing this thing.
I did try grid fill and checked Youtube how to use it exactly. Still did not get it to work.
Annoying being so new and clueless, but I am not giving up 
I figured out the cause of the issue:
Still no clue how it happened though.
If you want to take a look, here is the file:
I’m not sure what happened, but about your first question, let’s say you have this situation:
Select these vertices:
Press Ctrl F > Grid Fill, and it fixes the topology:
I took a look at your file and it seems you just accidentally hid that one vertex. 
That is why it’s ‘fixed’ by applying the subdivision modifier. You can reveal hidden geometry with Alt + H.
That looks great, yeah. A lot better than my screw up
Thank you.
I remember I hit HIDE a few times.
It is fixed now though. I unhid it and applied the solidify and subdivision and it looks flawless.
Thank you very much for the help! Much appreciated.
I didn’t know modelling was fun before
Might be overdoing the details, but that I guess it’s part of the learning curve.
When rendering in cycles there are some smoothing issues, I guess you could call it.
Is this due to the amount of detail I tried to add to the geometry?
we can’t guess, maybe show the wireframe
did you right click > Shade Smooth?
Some of the artifacts look like they might be related to an issue with cycles when smoothing (relatively) low poly geometry.
Try adjusting the Shadow Terminator Offset (Object Properties Tab > Shading) and see, if it helps.
Some of the small shading artifacts are probably caused by the poles (vertices that are connected to more than three faces, like on the dripping icing on the left).
