Might be a sign of fin rot. I'm no expert, it's just a hunch/guess. I'm not sure about treatment, but antibacterial medicine probably works.

Using Melafix and Pimafix as Nossie said will help real quick. They are natural remedies and should be kept in every "first aid fish pharmacy"    Tubi is a lovely fish, she's so pretty.

( our Humphrey had a broken dorsal fin once, it healed quick with using those two remedies and now you even cannot see it anymore where it was )

Oh as I mentioned I bought them 3 days ago they are often under the air pump and they sleep a lot is this normal?

Thats a very beautiful fish!

Thanks guys, I will try to get the water tested soon and buy the kit needed, and I bought 2 Goldfish Tubi and Bitski They are both eating, and they leave under the waterpump from time to time. They are always together following eachother My tank has about 35-40 liters... It's not too big.

I agree, unfortunately too small for 2 goldfish. You will need to upgrade in a couple of month  (... speaking here out of my own experience... ) as they will grow quickly and then problems will start to show.

And as already mentioned, very important to have the water tested and keep up to day with testing and waterchanges.
How big are they now?

Her tail will heal on it's own as long as you keep the water quality good! My fish have had some small rips from time to time, but they've always healed and I've never had to treat them for any illness
So you should definitely have the water tested, and do a large water change if needed. Remember to add water conditioner to the new water! If you want to, you could buy some medical aquarium salt, I use the brand Sera, so that probably exists where you live It can be combined with an anti-bacterial medication by the same brand if your fish would get worse in any way!

And another thing, it is possible to keep two fish in this tank, but for this to work, you've got to change the water very often to keep the nitrates down. This is why you need the test kit, because without keeping track on the nitrates, your fish will get sick and at worst, die. You also need to remember that they can't live there for too long, you have to buy a 100l for them as soon as you can! I managed to keep my fish in the same size tank for about 10 months, but I was constantly worried about them and they weren't feeling too good in there sometimes... So spare you and your fish the worries and try to save up for a bigger tank soon, there should be some cheap offers in your pet store I'm sure!

Common tap water's fine There are water conditioners available in the pet shops that will remove any chlorine and other toxic substances, not very expensive, and a medium bottle will last for pretty long

It would be quite the opposite if you would upgrade, because that way your tank would pretty much take care of itself! The bigger the tank, the easier to care for. If you have a small one, the tank will get polluted much faster, especially since you have two goldfish in such a small one.

How long would you be gone in the summer? There are those automatic feeders that you could buy. It's like a box that you place on top of the tank, dose some food in it, and it will feed them whenever you've set it to. But if you'd be gone for long... I don't think your fish would be alive when you come home, not because they'd starve, but because nobody would change their water, so they'd poison themselves

That's not good at all... Whenever they do this, you need to change a big portion (=60%) of their water, okay? Because that's usually a sign that the nitrates are too high, i.e. they're pretty much poisoning themselves. And I'm sorry to say that a 70 l isn't much better in this case, let alone the 60 :/
If you don't want to get a 100 l tank, you have to give away one of your fish, because they can't live for too long in that 40 liter you've got.

So give away one of your fish, if you want them to live for a bit longer than a year. Where's the joy of having them if you won't allow them the space needed? Believe me, a 100L isn't that big once it's set up and done!

And if you want a 54L, it's pretty much a waste of money to even buy it, because it will be the same as it is in this tank. 10 liters more won't matter since one goldfish needs about 40L to be healthy.

You mentioned in another post that you want to get a 60-70 l tank....well in this case I advise to go for the 70l but not for the 54l one.
Please believe us, we are here to help and what we advice has got very good reasons...

I believe you

And for pimafix and melafix: I tried 2 MAJOR pet stores they didn't have it 

A 70L is still not quite enough, but it's alright! You may just have to change water a bit more often but otherwise it should work. IF your friend would be offering something bigger, you should accept that though As long as it won't be too expensive for you!

We don't have Melafix here either (Finland) d: So maybe you can find it on the internet?

Wow I never thought goldfish need so much