The verb "يقدر" "Yuqadd-deru" = roughly means"to estimate / evaluate" (root: قدر). "قدره" = the word "قدر" "Qadr" = "estimate or value" (Noun of previous verb) with the enclitic pronoun "ه" = "his value". The word "حق" "Haqq-qa" = "reality / truth" (root: حقق). The expression :"يقدر (الشئ ) حق قدره" = "to evaluate / estimate (something) to its true value" Since the sentence is negative, "لا يقدر (الشئ) حق قدره" = he does't estimate (something) to its true value / degree" , in other words "he underestimates it". Full translation would be something like: فقلت في نفسي: إنه لا يقدر ما نحن فيه من الخطر حقَّ قدره وكيف له أن يدرك وهو لا يجوع ولا يعطش "I said to myself: He underestimates the danger we are in, and how would he understand ( / realize) , since he neither goes hungry nor thirsts". (in other words, because he doesn't feel hunger or thirst, he underestimates the danger they are in)

المعنى أنه لا يمكنه فهم ما هم فيه من مشاكل