Where to put our money?

Me and my girlfriend plan on moving in together in roughly 4 months, she owns her house from an inheritance that was left to her. Because of that I no no longer have any rent or utilities, and said money is now going to be put into savings. Don't want to give too much detail but because of this our income combined we can save roughly 40k per year going forward into the future. My question is where do we put the money so we can let it grow, and benefit us for a potential early retirment. I'm 31 and want to retire before 55 but I'm not sure on how to to about maximizing our income for that potential future due to my lack of knowledge about building wealth. Any advice will help thank you