can't boot on win10 without alt (option)

I don't know what happens but the issue is solved after a lot of reboot

When you installed Windows, you failed to set Windows as the default operating system to boot. In your case, there are two ways to do this.

• First, boot to the Startup Manager by holding down the option key, Next, select Windows as the default operating system to boot. This can be done by holding down the control key while selecting the arrow below the icon representing Windows. This arrow should change from a straight arrow to a circular arrow.
• Select Boot Camp on the Windows Control Panel. Highlight Windows to select Windows as the startup disk. Either exit the Control Panel or select to restart the Mac.

In your case, you knew enough to boot to the Startup Manager, but did not know you needed to hold down the control key. Also, you knew enough to open BootCamp from the Control Panel, but did not know you needed to select (highlight) Windows before exiting or restarting.