With my phone I can easily write English, French and Hebrew. But I'm wondering if there is a possibility to add vowels to hebrew words, as it's possible with a keyboard with Windows.
I was able to successfully type Hebrew with vowels on a Samsung using the steps I found on another forum:
Since a few weeks ago it became possible to type vowels in the Gboard app—Google's own keyboard. I strongly recommend it. I switched from Samsung keyboard to it.
To type the vowels, type the consonant first, and then hold down the letter that begins the name of the vowel sign:
Patakh, Hataf Patakh: פ
Kamats, Hataf Kamats: ק
Segol, Hataf Segol: ס
Holam and Shuruq go with the letter Vav, so hold down Vav (ו) to type them.
Dagesh is the same character as Shuruq, and it's available also on Dalet (ד).
Kubuts is on ק, together with Kamats, even though it's a different sound.
For Shin and Sin dots, use the letter Shin (ש).
A similar system exists on Windows since Windows 8, and on recent desktop Linux systems (since 2013 or so). Use the Alt key and the above letters to type the vowels.
For Kubuts, use \ (the backslash; mnemonic: it's diagonal, like the dots in Kubuts).
For Shin and Sin dots, use the Q and W on a QWERTY keyboard (mnemonic: they are above ש on the physical keyboard). For Hataf characters, use the key to the right of the letter:
Hataf Patakh: ]
Hataf Kamats: ר
Hataf Segol: ב