The 2 lower ones can be filled in with planar surfaces, after you delete each one, select the main object and run Construct > Planar to fill in the hole. Do those one by one so you don't open up a larger non-planar hole as would happen if you deleted both of them at once.

Then the upper one runs into some problem trying to do that I think because of a teeny tiny edge in this area here:






That little edge is only 0.0004 units long and something around that size under the fitting tolerance tends to get collapsed down and cause topology problems.

That may need to be dealt with by drawing in a line from its end and making a triangle on the left side there first, then the remaining area will probably behave better. Let me know if you're stuck with that part.

- Michael