Ibamos a encontrar para correr, pero no pudo venir, y terminé yendo yo solo. (sola if you are a woman)

"Estar" is the wrong verb here. In English you say "were going to" (verb "to go"), and so must you in Spanish with "ir a". That "se" makes no sense whatsoever.
"Correr" cannot be used as a noun, so forget "un correr". You can say "para correr", "una carrera" (a race), etc.
Here "no podía" is not right. You have to say "no pudo".
"Corré" is wrong. It must be "corrí".

Any feedback on previous questions you posted (and I answered)'

thank you very much, that makes more sense, yeah, I am trying to apply "se" here(meeting up with each other), I guess I still need more practice with "se"

lazarus1907 said:

Ibamos a encontrar para correr, pero no pudo venir, y terminé yendo yo solo. (sola if you are a woman) "Estar" is the wrong verb here. In English you say "were going to" (verb "to go"), and so must you in Spanish with "ir a". That "se" makes no sense whatsoever. "Correr" cannot be used as a noun, so forget "un correr". You can say "para correr", "una carrera" (a race), etc.

Here "no podía" is not right. You have to say "no pudo".

"Corré" is wrong. It must be "corrí".

Any feedback on previous questions you posted (and I answered)?

you answered it all, thank you so much

Aaah! I made a stupid mistake (too many self-corrections):

Íbamos a encontrarnos para correr, pero no pudo venir, y terminé yendo yo solo. (sola if you are a woman)
Nos íIbamos a encontrar para correr, pero no pudo venir, y terminé yendo yo solo. (sola if you are a woman)