Slitherine

Is it normal to attack a region, with almost five times more troops and a 1-2 general, and lose?

The previous turn I attacked in the same way, but with more troops and they had no general, the result was the same.

Number of troops have very little meaning on the outcome (exactly zero, if both already have full frontage worth of units present).

You seem to be attacking with a force of (mainly) heavy infantry on turn 148 (which is a harsh weather turn, as it is dividable by 4) in forest against a force of mainly medium infantry supported by a full frontage of skirmishers. If you didn't lose that kind of bad odds, it would be the 8th miracle of God. You were in essence running full speed head first into a concrete wall. If it hurts, guess whose fault it is?

I only have 6 units of heavy infantry, and the turn is good weather, that indicates in Spanish next to the date "Buen tiempo"

You seem to not even damage them, given the battle ends with all their units but one in green. So yes, there must be a bad combination of factors. You must watch the battle and see what happens in the duels to improve your game. There you'll perhaps see that the enemy general gives a bonus in forest, or that they have infantry with extra bonus. I would anyway remove all your heavies and attack only with medium and with your best skirmishers. If you start doing some damages, even if you lose, then try to attack several time a turn to wear them down (you need to attack from several regions).

I saw the battle and his heavy infantry was much better than mine, I carried more heavy infantry and attack from several regions, but my troops arrived at the same time, and although the results of the battle improved, I continued to lose, the next attack I did the battle with the FOG2 and beat with ease.

Thank you

Your heavy infantry is most probably not the optimal unit to fight in these conditions in any case. FOG II, the tactical game, handles terrains penalties differently indeed. As long as you had fun, that's good