The only way to master and play a sport to the best of your ability is PRACTICE, PRACTICE and more PRACTICE.
20 minutes of play time for 5 days a week is far too little to compete and give a fight against better players. You need to increase this practice time and make it more effective.
Find a player who is of your competence level in the sport and practice with him/her. Have a practice schedule: for example, one person can try out different spin serves while the other can receive it for the first 10 minutes. In the next 10 minutes, you can reverse roles. You can then move on to chops, rallies, smashes, etc. This helps keep the routine mixed so you don't get bored with one thing, as such. At the end of the practice session, both of you can have a match, where you can try out all the things that you might have practiced in the day.
When you don't have a table to play on, you can practice against the wall. Another way would be to for two players to play on a thin long horizontal stool/table, instead of the normal table. This will help you place the ball better and perfect your direction choosing abilities and the angles with which you play the shot, as the table is much narrower than the original table used in table tennis.