To Understand
To Comprehend
する verb
理解 is understanding, so the verb version would be...? How about to understand or to comprehend? Well, do you?
りかいする
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. Of course, if you know 理解 already this one is easy to comprehend.
お前が彼のことを愛しているのは理解するけど、あいつがお前にキスをするのは許せないよ。
I understand you love him, but I can’t forgive him for kissing you.