OK, what you're asking for is evidence of a common ancestor.
Before I break this down, I want you to understand something (and this thing is where the lunatics of this thread like to insert themselves. I'm breaking it down for you because you really seem like a person who is trying to understand):
Scientists do not have every answer for every question. This is OK and it is normal. It does not mean that Christians are right, it simply means we don't know yet, OK? Fossils are incredibly difficult to form and find, and the fossil record is robust, but there are gaps. Those gaps, again, do not mean Christians are right, it just means we don't know YET.
Keeping all of that in mind, modern humans (us, me and you and your family members) emerged about 300,000 years ago in Africa. Some of our species left Africa and migrated through Asia and Europe. Some of those branched off into their own species, like the famous Neanderthal. Black hoteps like to use this information to say that White people are Neanderthals or have Neanderthal DNA (and this is true) in an attempt at dehumanizing them the same way they did to us by calling us apes and monkeys. There is truth there, but they are attempting to weaponize it the same way White people attempted to weaponize evolution against us.
The truth is, Humans are a primate species. All humans, that included Neanderthals, which went all but extinct, and homo sapiens sapiens, which is the scientific name for humans.
As for our common ancestor with monkeys, well, humans "are monkeys" which means our ancestor was a monkey. The misconception is that we come from monkeys that are extant today; this is wrong-- monkeys that exist today are more like cousins to us. But cladistics state that you do not outgrow your ancestry, and because our ancestor was a proto-monkey (a PRIMATE), we are, too, primates.
There are plenty of examples of evidence for a species that was the in-between state of non-human primate and human, the most famous of which is Lucy
en.wikipedia.org
When you look at the remains of Lucy, you cannot distinguish her from a human or a non-human primate. She is a blend of both-- her hips suggest upright walking like a modern human, and modern non-human apes do not have this hip structure.
Lucy also has the rib cage of a modern non-human ape, which suggested she had a larger stomach and subsisted on mainly vegetation, like modern non-human great apes.
In other words, she is a perfect blend between the two creatures, humans and apes. She is therefore considered our ancestor, because we have her traits.
I can talk about this more at length if you'd like