Phenomenology has parallels to solipsism, but its a broad subject.
The basic starting point is that consciousness precedes reality.
Insofar as what you know is true, the first and most truthful thing you can know is that you are conscious. This is true be you awake or sleeping, it always is and always has been. You do not know if anything existed before or if there was a before, and you don't know it will ever end.
Everything else you can know after this, is less and less truth.
The experience you have day to day is truer than anything you believe in, but what you believe in affects how you experience the day to day.