Your situation is quite common place.
The good thing is that you wish to cultivate. You also have the blessings to believe in the Pure Land Dharma Door.
It is unfortunate that you do not know how to cultivate. That was why you made no progress in cultivation. It is not surprising that you were dejected because how can one continue if cultivation seems to have no real concrete benefits at all!
If you really want to cultivate, you should:
For example, I have a student who practiced Zen for over ten years. He then came to our temple to practice Pure Land. After less than a year total time of practicing with us, he realized that his level is higher than his previous Zen teacher.
Selecting a good knowing adviser is most critical to your practice.
In summary, you should resolve to actively seek a good knowing adviser. Every day, you should bow to Amitabha Buddha 108 times, seeking his guidance to help you find a wise teacher. You should also invest the time to visit the various temples to get a feel of the atmosphere, the attitude of the left home people there, whether or not the assembly is serious about cultivation, then you should get the temple’s own publications to see what kind of Mahayana they are teaching.
If you really follow the above-mentioned instructions, in the future the Buddhas and Bodhisattvas will eventually guide you to meet with a competent and wise teacher.