We stretch not ourselves overmuch (ou huperekteinomen heautous). Apparently Paul made this double compound verb to express his full meaning (only in Gregory Nazianzen afterwards). “We do not stretch ourselves out beyond our rights.”
We came even as far as unto you (achri kai humōn ephthasamen). First aorist active indicative of phthanō, to come before, to precede, the original idea which is retained in Mat 12:28 (Luk 11:20) and may be so here. If so, it means “We were the first to come to you” (which is true, Acts 18:1-18).