Hi @easyt50,
Thanks a lot for the link
I found that I made a mistake on the first install (all this is new to me).
On the first install, I tried to follow @Akito and @Leslie_Satenstein tips for partitions in the Ready for the Switch thread, but last night I realized that the disk was in MBR and not in GPT as @Akito mentioned, so I formatted the disk again, but now in GPT and after installation I got the same result - After choosing WIN in GRUB, ubuntu startup disappeared and not you can access Linux again.
I finished these tests very late and only tonight I’ll test your tip after reinstalling Linux again and then I’ll post the results here
Following @ElectricDandySlider’s suggestion to search on the It’s FOSS site, I found this @abhishek tutorial - Fix Grub Not Showing For Windows 10 Linux Dual Boot and I would like to try it too although I didn’t want to mess with WIN installation
Thanks for the support