The described behaviour often boils down to the usage of xdebug, enabled by default even with no client (IDE) listening to it.

XDebug is even off

Please recheck this, at best completly remove xdebug to be sure.

Further, check if you have any other profiling things installed and active, for example xhprof, blackfire, tidyways or other APM/profile.

The stated timings are really off, special for backend standard views.

Otherwise, this would mean a really really really bad and slow harddisk. Not sure about your complete setup, do you have your project (docroot) on some kind of external usb drive or network storage (mountend) ?

Another point could be, that you have disabled all caches by reconfigure it to the NullBackend - or at least some essential ones.

You could also try to switch to pdo_mysql if you are using mysqli as database driver, or the way around if that helps.

Don't know the insight how xampp/wampp is build nowerdays and the internal webserver/setup/php integration. In general, it could also be some timeouts, stacking, poolings depending on webserver and configuration.

Otherwise - you need to get some profile and profile which takes the time, at least casual TYPO3 installation should not have such timings - even with really lot of data and pages.

You could try to do the cache:warmup on TYPO3 v12 before trying to load it in the web:

vendor/bin/typo3 cache:warmup

for a composer installation (casual setup) - or

typo3/sysext/core/bin/typo3 cache:warmup