[4-Door Flunky]

If the linkage feels sloppy, it's because there's a little bushing on the shifter that needs to be replaced. I think it's supposed to have an inch of play. Mine is worn and has two inches of play.
The big reason it's hard to shift into the gears you mentioned is because the synchronizers are worn for those gears. I recommend double-clutching.
Double-clutching means that to shift from first to second, you clutch it to neutral, let off the clutch, and then clutch it to second. Truck drivers double-clutch every gear, unless they learn to rev-synch.
Rev-synching means you shift from one gear to neutral, and then from neutral to another gear...WITHOUT USING THE CLUTCH AT ALL! You do have to rev the motor up to the proper RPM first...
Truck drivers do that a lot. I don't recommend doing that with your BMW. I tried it on mine, and ground the synchronizers a little before I decided to call it quits.
And I'm a former truck driver, too!
But I'd recommend just driving the hell out it, and not having your transmission rebuilt/replaced until won't go into any gear, or won't come out of one. Practice the double-clutching. I know one guy with half a million miles on his transmission who has been double-clutching every gear since he's had it.
Flunky
PS-Double-clutching is easier on the transmission and clutch...but it's slower. Most people never do it unless they're driving a truck...or a tractor.
PPS-When Vin Diesel mentions double-clutching in The Fast and the Furious, he's just being an idiot. He doesn't know what it means.