Looks like this is a part of your problem.
traceroute / tracert should work.
D:\temp>tracert -4 acme-v02.api.letsencrypt.org.
Routenverfolgung zu ca80a1adb12a4fbdac5ffcbc944e9a61.pacloudflare.com [172.65.32.248]
über maximal 30 Hops:1 <1 ms <1 ms <1 ms fritz.box [192.168.0.1]
2 4 ms 5 ms 5 ms 62.155.240.117
3 7 ms 6 ms 6 ms 217.239.55.2
4 6 ms 5 ms 6 ms 217.239.55.2
5 7 ms 6 ms 6 ms lag-10.edge4.Berlin1.Level3.net [4.68.73.5]
6 7 ms 6 ms 6 ms ae-1-3502.edge3.Berlin1.Level3.net [4.69.159.1]
7 6 ms 6 ms 8 ms unknown.Level3.net [212.162.40.34]
8 6 ms 5 ms 6 ms 172.65.32.248
Last year Letsencrypt switched to another CDN solution.
A lot of topics with such connection problems, reducing MTU sometimes helped.