One will know that Allah is happy with him when he does what Allah wants and continue to do it out of steadfastness
Reference : chapter the Believers. Kindly go through the chapter and it will tell you what behavior makes Allah happy.
2. You will know if you don’t go back to the sin or the like of it. Also if you continue to ask for forgiveness.
Hadith says: Someone who repents from sin is like the one who has never committed a sin and the one who always ask for forgiveness is loved by the most Merciful”