I believe when God says "the beginning"... it was the beginning.
This naive approach doesn't work in scripture because "the beginning" never refers to the starting point of the Universe or planet Earth as we know it today. In fact, "the beginning" doesn't always refer to the Genesis creation either (e.g. Genesis 10:10; Psalms 111:10; Mark 1:1, etc).
When God says He created everything in six days...I believe He created everything in six days. When God says death entered the world through Adam...I believe death entered the world through Adam.
When God says He created woman from Adam's rib...I believe God created woman from Adam's rib.
When God tells us He created Adam from the dust...He means it.
Etc ...
Other Christians believe this too. However, it doesn't logically follow that believing in the "six days of creation" (Exodus 20:11) requires your misunderstanding of what the Genesis creation was referring to. According to scripture, the "six days" followed after the Land was already covered with "darkness" and "deep waters" (Genesis 1:2). The apostles also understood this (2 Peter 3:5).