Need help with HSTS header

PS: You have 6 active certificates, two created today - https://check-your-website.server-daten.de/?q=klimatfokus.nu

CertSpotter-Id Issuer not before not after Domain names LE-Duplicate next LE
921726979 CN=Let’s Encrypt Authority X3, O=Let’s Encrypt, C=US 2019-05-20 10:46:12 2019-08-18 10:46:12 klimatfokus.nu, www.klimatfokus.nu
2 entries duplicate nr. 4
921413238 CN=Let’s Encrypt Authority X3, O=Let’s Encrypt, C=US 2019-05-20 06:44:47 2019-08-18 06:44:47 klimatfokus.nu, www.klimatfokus.nu
2 entries duplicate nr. 3
918243369 CN=Let’s Encrypt Authority X3, O=Let’s Encrypt, C=US 2019-05-18 07:21:36 2019-08-16 07:21:36 klimatfokus.nu, www.klimatfokus.nu
2 entries duplicate nr. 2
917043841 CN=Let’s Encrypt Authority X3, O=Let’s Encrypt, C=US 2019-05-17 14:11:29 2019-08-15 14:11:29 klimatfokus.nu
1 entries duplicate nr. 2
915386386 CN=Let’s Encrypt Authority X3, O=Let’s Encrypt, C=US 2019-05-16 16:00:25 2019-08-14 16:00:25 klimatfokus.nu, www.klimatfokus.nu
2 entries duplicate nr. 1
915317695 CN=Let’s Encrypt Authority X3, O=Let’s Encrypt, C=US 2019-05-16 15:06:23 2019-08-14 15:06:23 klimatfokus.nu
1 entries duplicate nr. 1

As written. It’s not a certificate problem.

Use one certificate 60 - 85 days, then create the next.