Ubuntu – Grub2 add entry for Windows 7

I have installed Windows 7 and Ubuntu 16 and I can see both on the bootloader, however I can only start Ubuntu. If I choose Windows in the bootloader it shows an error message and then reboots the computer. It seems like the Windows link is broken on the bootloader.

$ sudo fdisk -l
Device     Boot        Start        End    Sectors   Size Id Type
/dev/sda1               2048   97656344   97654297  46.6G 83 Linux
/dev/sda2  *        97656832 1949212671 1851555840 882.9G  7 HPFS/NTFS/exFAT
/dev/sda3         1949214718 1953523711    4308994   2.1G  5 Extended
/dev/sda5         1949214720 1953523711    4308992   2.1G 83 Linux  

Device         Start       End   Sectors  Size Type
/dev/sdb1       2048    206847    204800  100M EFI System
/dev/sdb2     206848    468991    262144  128M Microsoft reserved
/dev/sdb3     468992 151764991 151296000 72.1G Microsoft basic data
/dev/sdb4  243890176 250068991   6178816    3G Linux swap
/dev/sdb5  151764992 243890175  92125184   44G Linux filesystem

It seems like the init is sda2 which is the partition with my Windows data, however the Windows OS is in sdb3.

The Boot Repair Boot Info Script generated these results.

I have installed boot-repair, but it says that it does not work in Legacy Mode, only in UEFI.

Also I have added these lines in /etc/grub.d/40_custom and updated grub, however these entries do not let me boot Windows 7 either:

menuentry "Windows 7aa (loader) (on /dev/sdb1)" {
insmod part_msdos
insmod ntfs
set root='(hd1,msdos1)'
chainloader +1
}
menuentry "Windows 7bb (loader) (on /dev/sdb3)" {
insmod part_msdos
insmod ntfs
set root='(hd1,msdos3)'
chainloader +1

What else can I try?

Also I have tried

sudo update-grub and sudo update-grub2

Updated:

Windows entries in grub show me this error "The partition does not exist, press any button to continue…" and then again the grub menu appears.
I have tried adding a new Windows entry for the Microsoft reserved partition /dev/sdb2 (hd1/msdos2) and it shows a different screen:
Boot loader Windows administrator, choose a O.S. only with Windows option, if I choose it, then the computer reboot.