Help!!… Great Dane Training..?

I have a 13 week Great Dane mix.. She's 1/2 Great Dane and 1/2 Bull Mastiff...
She's a really sweet dog, but she just does not listen! She understands that we someone says "NO!" that she's not supposed to do that or go there, but sometimes she still does... I know that you're supposed to use positive reinforcement with danes, but sometimes it gets so annoying that I'll yell or tap her on the butt real lightly... but for the most part I just clap my hands real loudly..

Oh she also runs away sometimes when I try to bring her back...

PLEASE!! If you know how to help ANSWER!!

Thank You!! :)
Thanks for all ya'lls help...
And yes I realize that Harleigh is still just a young pup.. I guess I just forget cause she's so big! haha..

If you have any other training tips that may help.. You are more than welcome to share them with me! ;) Thanks again!