Speed is one of the easier skills to get.  It will come with practice, quite reliably.  In fact, it is easy to end up playing any instrument too fast.

Don't worry about "keeping up" in the sense of matching another player note for note when jamming.  Even a fast song can work well with one or more instruments pulling some longer slower notes.  Find something easy enough to be able to play it that sounds like it fits.  You can work on faster bits and more complicated bits later.  Focus on getting it to sound good when jamming.  Speed will come.