You can always speed up skills you've already learned. Turning down the gamespeed will just make you a worse player in the long run. Okay, turned a little longer than I thought. If nothing else works, at least figure out what the computer is doing. As a huge added bonus, anything you take creeping is one less thing the computer will get. I usually play Night Elf and if I can get my Demon Hunter to 6 pretty quick I'm going to wipe the floor with the computer. A high level hero can make a world of difference. Creep with your hero like crazy as soon as you can. He's basically a knight, can be a very decent healer, and has a damn good short term aura type ability (Roar). I'd consider voting the Druid of the Claw the best single unit in the game. And try to keep them the same between games so you get used to them. Run into an unexpected enemy and your archers are in the thick of it? Hit '4', run them back, and attact the single flying unit that only they can hit.
![warcraft 3 peon warcraft 3 peon](https://i.ytimg.com/vi/Ii3oDn5iTt4/maxresdefault.jpg)
That way you can pull the right people to do the right job. Have the hero in the group assigned to '2'. Use the group hotkeys! And I don't just mean assign your main group to '1'. Read and memorize the best build order for your race. My brief recommendations (hey, it's late): I breezed through the campaign and can have a hell of a time beating the computer on even a small map. The computer can play pretty damn well in custom games.