Good match in my opinion but you were playing a little too safe once you went true hero. With true hero against true hero you have to try and get the opponent to exhaust all their moves or bait out a counter. A good trick to do is to dashjump and use the spear 1 as the guy was doing, Great match though! Just remember to play aggressively on true hero undyne
It could either be a shorter match or a way longer one depending on their approach. While true hero does sacrifice 75 health, it offsets that by giving you an enormous defense