Edit: You added the quote in an edit, which is different from the one I thought you meant by "Einstein's famous statement about the importance of bees". In my defense, I would still consider the quote I listed to be Einstein's famous statement about bees (it's the only quote you'll find in the Google search results for "Einstein bees").
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I forgot to link Quote Investigator before: https://quoteinvestigator.com/2013/08/27/einstein-bees/
It's as close to conclusive as you can get for any quote misattributed to Einstein (and there are hundreds of quotes misattributed to him). You can't prove someone never said something. At best, you can prove someone else said the same thing earlier.
As for whether it's true,
1) You won't find any scientific study or any evidence supporting it. It was just made up.
2) The evidence against it is that the vast majority of our food doesn't require bees. Grains and staples like corn, wheat, rice, and soybean aren't pollinated by insects. Meat doesn't require bees either, as animals tend to be fed grains or grass. Vegetables generally don't require bees. Many fruits can self-pollinate or aren't pollinated by bees (bananas, citrus fruit, etc.). Finally, even the fruits for which bees are currently essential (kiwis, watermelon) could be manually pollinated if necessary. But even if we lost those few fruits and nuts entirely, humans wouldn't go extinct in 4 years (or at all).