I always mess up on the bottem. how do i make it smooth and not lumpy or messed up?

im not a pro or anything but i just make sure that there is plenty of extra fondant hanging over the bottom of the board and use my smoother to get it even and smooth. then i cut off the extra with a pizza cutter and go over it again with the smoother

maybe someone else will have some more tips for you
HTH

thankss for the advice ima try that way

By lumpy do you mean the buttercream under the cake has shifted or do you mean you have pleats around the sides?

If it is gathers or pleats where the excess fondant was, one thing I have found is that it helps to pull the fondant away from the cake as you are smoothing it down. I also work around the top section of the cake, then move down another inch or so and work that smooth all the way around then keep going until I am at the bottom. That way you don't get to smooth allt he way around then have a big section of extra fondant to deal with.