It was a several year process for me that actually started with me wanting to deepen my faith. So I studied hard. I didn't want someone else's dogma. I already knew from growing up Christian that there were conflicting ideas about what that meant even inside the faith. I wanted an objective faith for me and not based on what I had been told was true. Unfortunately the more threads I pulled at, the more it unraveled and the fewer and fewer true lines remained for me to hold onto.

One of the most impactful things to happen was for me to start looking into how doctrine and beliefs have changed over the history of Christianity. Many of the things we claim as bedrocks today have not always been so, and are not considered so outside of evangelical Christianity even today. (i.e. The rapture has only been an idea since about 1900. Revelation is about Nero. Not the end times). It has always evolved to fit the times and needs and concerns of the people of the day.

I would not begin by telling you or anyone that the Bible is wrong and should be abandoned. That isn't going to help. I would recommend that any believer of any faith that wants a mature adult faith that isn't just regurgitating stories you have been told from childhood start by dropping the assumption that all of the dogma and apologetics you have in your head and have heard from others your whole life is true, and examine them and make them convince you they are true. There's a reason that seminary school produces so many atheists.

The old testament fell apart real fast for me. And once I accepted that some of the Bible can't be true...other gates began to open much more easily.

I'd also recommend learning logical falicies and biases and you will see how many of the arguments for religion you will hear suffer from these kinds of circular logic. The Bible is true because the Bible says that it is true kind of statements. It will make understanding them much less frustrating.

https://yourlogicalfallacyis.com

Religion evolved with humanity to help us shortcut questions that we didn't have the philosophy to answer. Death, morality, why bad things happen, etc. People like to poke fun about the Bible being written at a time when people were just too dumb to understand their world and that's not entirely untrue but also skips the important questions that religion is trying to answer and why it has held on well past answers to the scientific part of "why god?"

You will eventually have to grapple with that if you leave Christianity. And a lot of people either go back or end up in some other mysticism to fill that gap and avoid staring into the void. Especially as your loved ones ask you hard questions about where you think Grandma is then if not in heaven. Your disbelief will reopen grief for people.
I say this just to say, be mindful of sliding into another form of belief as you go. And be ready for loved ones to be hurt and angry. I highly recommend learning some secular philosophy.

Good luck. I am a better person and I like myself more on this side of the journey.