"Today I went running. It has been such a long time since I last went running." :)

Your question should be: Could you please correct the following sentence? and the sentence(s) should be: Today I went running. It has been (or It's been) such a long time since I last went running. And a tip? Try inventing a couple more sentences following the same format, and repeating them to yourself. Today I *****. It' been such long time since I last ********. It'll help fix the construction in your mind.