How to play multi-pawn endgame?

The following screenshots are positions I lost these days.

Accoding to engines,in position 1, I lost after I play  Kc4,and in position 2, it is actually slightly better for me(engines say that) ,but I finally  lost again.

Are these multi-pawn endgames  hard to play? I have no idea.I think I lack enough knowledge to deal with  these positions.Can someone give me some advice? Both on these potisions and/or recommend me some materials 

(Actually ,I have Dvoretsky's Endgame Manual and I am reading this book these days,that makes me even more depressed after losing the  similar endgames in a row)

Dvoretzky's Endgame Manual is an excellent book. It provides answers to your questions, but it takes time to study it. Do not study more than one endgame at a time. Quality > Quantity.

First position. This is a pawn endgame. Pawn endgames are all about calculation. In this case black has a passed pawn f5 and a candidate passed pawn g5. You apparently want to approach b5 with your king, win his pawn a5 and queen your pawn a3. However black is faster with his f- and / or g- pawns. So your king has to stay in the square of his most advanced pawn.

Second position. This is still a middle game: 2 rooks + 1 bishop each side. White is a pawn up, but bishops are opposite colored. Pawn a4 is a dangerous candidate passed pawn.

Only calulation is not enough for the first positon, one must know the key point of this position.

I rethink this position and  here are my thoughts:  if black f-file pawn is on the fifth rank,if the black king can move to d5,he can win the game. This makes a4 the only move for white to get a draw.

For the second position,I still have no idea how to expand advantage for white, maybe I should just push my own past pawn.

#3
Position 1: Indeed a4 is the good move to draw.
Position 2: Indeed d4 is the most logical move for white. It looks like a draw.