Hello. What can I do when the temperature is over 25 degrees Celsius? Should i move my Acer Palatum a bit in order to prevent leaf burn (sun scorch) ? Or just let the bonsai in full sun and move on?

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...25 is not hot at all...
In my opinion leaf burn is caused by not giving enough water. That being said, my only maple is in the shade in the afternoon , but gets full sun in the heat of summer until about 15h.
..and do not bring it inside and then out again, Its a tree!!!!

Water is the coolant that trees need. If it has enough water at the roots the leaves will not burn, 25C is not that hot, all my Maples are in full sun during the summer and do not suffer any scorch.

just leave it outside if it only gets 25. And even if it gets warmer.. Protect from midday sun and keep well watered especially if temps go towards the 40

Several have noted, correctly, that the leaves will be fine.

One consideration when the sun is shining strongly is the pots. If the pot is dark colored (most are) it absorbs heat and can burn the roots. It can also dry the soil out pretty fast.

25 isn't hot, but 35 might be hot enough to matter. Water them a lot.