Hello Andreas;
Yes, you are right. The first two certainly are Tughras -Sultan Tughras. Likely, Mehmed V, if it is from the WWI period. To identify them, Tughras are individual and the detailed line work could be compared to known Sultan Tughras.
Otherwise, if the date of the saber's construction is known, then the Turghra would belong to the Sultan who ruled at that time period.
(However, from the small amount of the construction/decoration that you are showing us, I think this saber was likely made during the 1909-18 era.)