Are you combining your power-ups? Like crossing a rainbow ball with a round bomb or a rocket with a paper plane? Combinations like these are the key to completing the levels without buying items like hammers or more moves. A friend of mine was having trouble until I mentioned this to her. She said it never really occurred to her to try to combine the power-ups. Once she started doing that, she began completing levels more quickly.
As Graylady said, having a baseline of challenge to the puzzles slows people down. Also, enticing players to buy gold coins so they can get more moves for a difficult level is how Playrix makes their money with match-3 games. Playing without spending money is doable, but it is going to take longer, which is by design. Homescapes' October update will give us daily login rewards, so you can probably pick up some free gold coins, power-ups, hammers, and extra lives with that, which will make things a little easier for you.
