It doesn't work because ItemFood only has fields available to store details about a single potion effect, so when you set regeneration you're overwriting blindness. If you want to have multiple potion effects on your food item, you'll need to take a different approach.
The simplest way to do this for a single item would be to override ItemFood#onFoodEaten and apply the blindness and regeneration potion effects to the player from there. Or if you want a more extensible solution that you can use for multiple food items, you could create a collection of potions and an addPotionEffect method in your item class, and then use onFoodEaten to apply all the effects in the collection.
The setPotionEffect method takes 4 parameters - potion id, potion duration, potion amplifier and potion effect probability. You're using a probably of 1 so you can ignore that one, which leaves 3 parameters you're interested in.
The onFoodEaten method uses the values stored in the class fields which were put there by setPotionEffect, and uses those to apply a potion effect to the player.
What you need to do is change the call to addPotionEffect in onFoodEaten to use parameters that you'd previously passed to setPotionEffect instead of the class fields. And you'll need to call addPotionEffect twice because you want to add two potion effects to the player.
Can you give me an example please ? In my programm if it's possible
You've not said which of my two suggestions would be most appropriate for your scenario, but if it's the first one then the code is so simple that if I were to give you an example in your program (which is called a class, incidentally) I'd have essentially written it for you and then you won't have learned anything.
I've explained exactly what you need to do, make an attempt at it and if you get stuck or can't make it work then post your code here and I'll help you figure out where you went wrong.