I bought an SSL certificate because the one I had expired. How can I update this in letsencrypt cert bot,nginx?

I have 4 .crt files. Is it possible to simply overwrite the ssl in the existing example.pem file? Then I simply reload nginx?

What I mean, so here's the old example.pme file:

-----BEGIN CERTIFICATE-----
pQAABAMARzBFAiEAtVUqdO5TvjFCWA2a/xo6TazLWI8ZJkOLx5/frToDLkgCIERW
W3ZxyNB7CP91DiNRJEsKJ9qu8fHv7sbqKGzlPXgwAHYAIkVFB1lVJFaWP6Ev8fdt
huAjJmOtwEt/XcaDXG7iDwIAAAFzpdCu0gAABAMARzBFAiBKo45S3xgIa9BXAlw1
HWUFvbotsD+bmDqkuTsPLIK7xwIhANsUGH9r8ZRFCbbRkwZLV7aVgIH42Xgs4y3F
fDHfYxbgAHUAQcjKsd8iRkoQxqE6CUKHXk4xixsD6+tLx2jwkGKWBvYAAAFzpdCu
-----END CERTIFICATE-----

in this example.pme file, I would simply delete the old ssl and copy the new one. And after reload nginx.

In the example.pem file, I overwrote the old SSL with the new one, then reloaded and restarted nginx, but the browser still says that ssl has expired. What could be the problem?