Translation:I do not have the energy to run any further!
Added that now. Both work well, though. Quoting Oxford here:
[...] where the sense is ‘at, to, or by a greater distance’, there is no difference in meaning, and both are equally correct. Further is a much more common word, though, and is additionally used in various abstract and metaphorical contexts, for example referring to time, in which farther is unusual [...]
OK. So the British usage is a little different from Midwestern U.S. The definitions of farther and further are the same for us as what is stated in the Oxford Dictionary, but "farther" is the more common word. We almost exclusively use "farther" for distance and "further" in more abstract contexts. When referring to time, we use "longer" instead of "further." So "further" is a much less used word here overall. But that might be different in other parts of the U.S.
-Jon-Snow- Re: "Jag orkar inte springa längre!" Take a look: https://www.merriam-webster.com/words-at-play/is-it-further-or-farther-usage-how-to-use.