<human>: Can you condense the text into three sentences or less?

I'm currently a student going to college full time. I have a 7 year old Shih Tzu/Poodle mix that I love very much but just doesn't have enough energy for me. I bring her to the dog park maybe once a week or less because she doesn't seem to enjoy it. Doesn't play with other dogs and kind of just lays by my side. Of course I run her as much as possible but the energy isn't there (maybe it's age at this point). 

Iv always wanted a bigger dog. Something that I can "wrestle" with and not be afraid of hurting it, haha. I'm a pretty active person who can easily go on longer walks and show the dog some love. 

The only problems are, I'm not sure what to expect from this high-energy beast. What types of "puzzles" should I keep around for busy work? I'm sure it's going to be helpful with the other dog to accompany him but what am I getting into?

If you guys have any more breed recommendations, please let me know! Iv read up on these guys as much as I could (without opening a book). So any info is great.
<bot>: looking to get a Belgian Mal as a second dog. Looking foward to having something big to toss around but want to know other options and peoples experiences.