How can one restore faith and strength after a series of harsh experiences and divorce, and a feeling of being lost and returning to some bad practices, knowing that God tests those whom He loves?

Do not lose hope; as long as your soul is within you and your heart beats, repentance is accepted as long as the servant has not started to gurgle (at the point of death). You are strong and you will rise, and the strong believer is more beloved to Allah. Falling does not mean surrender, but rather an opportunity to rise and return to Allah, as Ibn Taymiyyah said that calamities require patience, contentment, and submission to Allah.

Trials are a test that reveals the sincerity of faith, and Allah does not want you to meet Him except upon Islam. Returning to Allah is the path, for Allah rejoices at the repentance of His servant and replaces evil deeds with good deeds, as He says: "Except for those who repent, believe and do righteous deeds. For them Allah will change their evil deeds into good ones. And Allah is Oft-Forgiving, Most Merciful."

Seek Allah’s help with your past through repentance, remorse, and seeking forgiveness, and commit to good deeds in your future, for true life is your present time. Strive for righteous companionship, and move to a place that helps you achieve righteousness if you can. If Allah knows good in your heart, He will grant you good.