Welcome to the forum. You have my condolences losing your husband, I lost my brother last year and we where support for each other our entire lives. When I needed my brother he was always there for me and same with me for him.
I am late to this thread, but I will have to say the same thing other have already said. Your tank is too small for an Angel Fish and this causes aggression. I have a 55 gallon which is about twice the size of your tank with two beautiful veil tail angels in it. And they are aggressive to my red eye tetras. My angel fish have already killed one, but luckily I have a big enough tank so well planted that the tetras can escape into the plants and avoid the angels. But the angel fish keep them pinned to one side of the tank. I am setting up a new 29 gallon tank which is close in size to your 100l tank for re-homing the tetras soon. Like I said, I can't add anything that hasn't already been said here, except to say I wish you the best and hang with the people on the forum, they can teach you everything you need to know about fish keeping.
I will leave you with one math advice on an easy way to change liters to US gallons and vice versa. I say this because in the future you will be reading threads here where the aquarium tanks will be stated in US gallons and you are used to thinking in liters. Others can correct me if I am wrong on this.
1 US gallon approximately equals 3.8 liters. So keep the 3.8 number handy. When I say I have a 55 US gallon tank multiply 3.8 by 55 and this will result in approximately 209l. Or take 100l size tank and divide it by 3.8 will result in approximately 26 US gallons.
Sum up:
Liters to US gallon divide by 3.8 - 100l / 3.8 = 26 US gallons
US gallons to liters times 3.8 - 26 US gallons X 3.8 = 98.8 liters which is rounded up to 100l
Like I said it is approximate number 3.8, just makes conversions a bit easier.