Is someone who tries to be diligent in performing the five daily prayers and makes up for those he missed due to work considered a disbeliever, and is it permissible to marry him?

"One who abandons prayer is considered a disbeliever (kafir) according to the soundest opinions of scholars, whether they abandon it completely or pray sometimes and abandon it at other times. This is the view of some scholars and is narrated from a group of the Companions. However, others, including Sheikh Al-Islam Ibn Taymiyyah and Sheikh Ibn Uthaymeen, believe that one does not become a disbeliever unless they abandon it completely.

Work is not an excuse for delaying prayer beyond its prescribed time. If the suitor delays some prayers, it is not advisable to marry him because he is considered a disbeliever by some scholars, and a sinner who has committed a grave major sin by others, based on Allah's saying: (Then, there succeeded them a posterity who neglected prayers and pursued lusts. So, they will meet Ghayy (i.e. a terrible punishment in Hell-fire)) Maryam/59. However, if he repents, declares his intention to perform them at their due times, and becomes upright in other aspects of his life, then there is no objection to marrying him."