Learn the Rules
I had difficulty with 3E when it first came out, just as I had trouble when I first learned AD&D. In comparison, 3E (and especially 3.5) is remarkably streamlined. Just practice some more and it should get easier. Fortunately, the basic rules system has been so well hammered out now that we don't have to worry about a bunch of new rules in DRAGON every month throwing monkeywrenches into our game, like we did with previous editions. Just options that use the current rules. So learn those, and you should be fine.
I had difficulty with 3E when it first came out, just as I had trouble when I first learned AD&D. In comparison, 3E (and especially 3.5) is remarkably streamlined. Just practice some more and it should get easier. Fortunately, the basic rules system has been so well hammered out now that we don't have to worry about a bunch of new rules in DRAGON every month throwing monkeywrenches into our game, like we did with previous editions. Just options that use the current rules. So learn those, and you should be fine.