Question regarding how old humans are

Hello.. I'm an ex Muslim and I'm slowly getting to know Christianity... I have one major doubt.. so if we trace the lineage back to Adam we see that Adam was made about 6000 years ago.. But science says human lineage is millions of years old and homo sapiens are about 300K years old.. so is there an explanation to this? I asked the same question when I used to be a Muslim and they simply told me don't question god's creation blah blah... but according to me a solid answer to this will be really convincing for me..