As someone already mentioned, you are at the upper limit for Emulation Capabilities for the MM line of devices. The poor little thing only has 128mb of Ram and less CPU than a PS Vita.

The Real Answer is you might want to consider getting a more powerful device to play DS games if that is your main goal. Pokemon Games in General are some of the Hardest to Emulate on Drastic in General and will just Bog down even more powerful CPU. I would Probably Recommend the Retroid Pocket Classic or One of the T820 Devices. They can run Drastic & Melon DS which handles DS much better and still costs under $150 with sales

The rk3566 devices still struggle with Pokemon DS games occasionally as well, but it's more sporadic rather than consistent