@eyyup_dogan - some thoughts/questions…
Do you prefer to have a drag and drop or perhaps a click the letters style of interaction?
How are you checking for the proper answer?
My approach to spelling types of interactions is to use an array to build the response.
In this manner - each letter that is selected is pushed to the array.
After the final letter is chosen - we join all the letter entries and compare it to the desired answer.
There are some other methods for checking as well such as assigning a unique numeric value to each different letter and using them as a check digit with some sort of algorithm to make sure the correct letter is in the right spot.
I recently did a spelling interaction but used clickables to make the words.
You can see that example at the post below. I think what you are attempting to do could be a modification of what I did there.
Animal Spelling - Trial Mode Testing