How to repeat 2 same questions for 84 different message??

Perhaps the quickest method then is to create an initial block containing an empty Text/Graphic item for the text to be rated, and the 3 questions. Then use the Copy option of the block 83 times. Copy/paste the 84 texts into the 84 Text/Graphic items, and put the 84 blocks in a randomizer in the survey flow. (This is the manual solution but using copy saves some time from having to create all questions one by one.)

A method that would use loop & merge is the following:

Create a single block that contains 84 Text/Graphic items containing the long messages. Below those, add the 3 questions you want to ask about those messages. Activate Loop & Merge on the block and set it to repeat 84 times, and check 'Randomize loop order’.

Then add display logic to each of the 84 Text/Graphic items. The first one should be displayed if the Loop & Merge current loop is 1, the second one if the Loop & Merge current loop is 2, and so on.

This way, on each Loop & Merge iteration, one of the long messages will be shown, together with the 3 questions.

I am not sure if this is a large improvement over the manual option. A disadvantage could be you end up with a single block containing 84 long messages.

Of course if you want to edit the three questions later, then this method ensures you only have to edit them once. With the ‘copy block’ approach you would have to edit them 84 times.