I’m trying to use Face > Fill Grid, but Error tells that I should select Two Edge Loops. I’m trying to fill sheet made of 4 meshes representing edges (previously converted from 4 curves) - similarly how it made here. .
I find with grid fill, if you extrude the edge inwards a little, and then use grid infill, it works a lot better.
I think that you need to merge that 4 meshes into a single mesh, before using Fill Grid 
It tells the same, but 1 time instead of several.
May be. But I want to understand how to use grid fill and why those error appear.
Try selecting 2 loops of edges/vertices on 2 opposite sides and then try again. I think the loops also have to have equal amount of vertices each.
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Try selecting all the points, then run Merge by Distance.
I made it. Yes, they have to have equal amount. Thanks!
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