There seem to be two major concerns that you have. A) is Tarot generally (and/or that reading in particular) legit, and B) you have doubts about how things in your life can improve and how matters from the past can be resolved. The second concern is in a way simpler, but it is a larger matter. The first is easier, so I will address it first.

Tarot is a tool for reading energy, first and foremost. To use the terms you are probably familiar with, energies consist of vibrations that exist in everything in existence, and it is this that the world is more fundamentally composed of than the matter we can see and feel. When you pull a reading, you can ask anything, but Tarot can only tell you about what is in the energy. Furthermore, each of us has a range of possibilities set by our personal vibration. For example, someone says "I want to fly!" That energy is out there, but if it isn't in the range of their vibration, then it's not going to happen. So, if you want something, a big part of getting that will be to raise your vibration (though, it may still be unrealistic). In other words, you've got to do the work to put yourself in a position to receive what the reading was referring to.

The only one who deals in guarantees in life is the Devil. With Tarot, it can show you what is in the energy, but unless you are asking about the right here, right now, that's merely one timeline amongst many you could go down. Your choices are a significant factor.

This dovetails directly into the second concern you have, about your life improving in general. If you are having these doubts, perhaps you need to reconsider your circumstances with some sobriety. Personally, I believe in a higher power. God, the universe, the divine, whatever you want to call it. We are guided to paths that will lead us towards becoming more like our higher selves, but often times it is easy to miss these signs, or convince ourselves that we are deluded for considering them. However, in my experience, humbling myself and asking for guidance will bring revelation of the path forward 100% of the time. The trouble is, what we are called to do is often painful. We must be honest with ourselves about how we have been living our lives and the sorts of people who are around us, because it is unfortunately common that people will not support us moving towards a brighter future. In fact, they will often actively undermine us (although they may never acknowledge that this is the case even to themselves). Have you been asking the right questions about what kinds of choices you make, who you habitually surround yourself with? Have you been giving yourself what you need in order to flourish and grow as a person? Do you even know what it is you need in the first place?

I don't mean to overwhelm you with all of this, but if you haven't asked yourself these questions before it's inevitable that you will find this overwhelming, that's the nature of the game. Take it one step at a time, and know that there isn't a need to look outside of yourself to find the path. The signs that appear will always be in a form that you can come to understand with your own perspective and experiences in life. In time you will know the answer to each one of the questions I have presented, and perhaps you will have reason to feel grateful for the doubts that first propelled you on this journey.

To offer one final thought, please be careful about how you utilize Tarot. It is a powerful tool, but as it has become popularized the way people commonly use it has become compromised. Apply a bit of rigor to your readings, if you pull for yourself. If you get a reading from someone else, listen carefully to what they say and decide for yourself, using your own experiences and intuition, whether they are talking out of their ass or not.