1.  실행 does not mean to run, nor is it a verb.  It is the sino (chinese root; look up native korean words vs sino korean) noun for "implement, put into practice, action, etc."  However, if you add the verb 하다 to any sino nouns, it becomes a verb.  Example 실행하다 = to implement (something)

2.  Verb conjugation is one of the most difficult parts to learning Korea--being a SOV (subject-Object-verb) language.  Where the verb is always at the end of a sentence.

For the purpose of verb conjugation, I'll break down a few sentences using the verb, to run.

달리다 = the verb to run (dictionary form, most basic form)

제가 달려요 = I run (present tense)

제가 달렸어요 = I ran (past tense)

제가 달리고 있어요 = I am running (present progressive)

제가 달릴 거예요 = I will run (future tense)

달리기 = running (gerund form) >> 제가 달리기를 좋아해요 = I like to run.

Have fun!