Welcome to the hobby and the forum.
A 45 litre aquarim is approximately 12 US gallons [I think better in gallons
]. You will have some problems with your proposed stocking, both in terms of number of fish and even worse the different species. Some of these are not compatible.
The rainbow shark with a mature size of 6 inches will quickly outgrow this space. And they can be territorial and aggressive, especially with other bottom fish. I would recommend you exclude this fish from your list.
I don't know what a "Fighter" fish is--do you mean a Siamese Betta? If so, no to that with most of the other fish. I think most beta keepers would recommend solitary or housed with suitable bottom fish, but they can comment accordingly.
Chocolate gouramis are acknowledged as one of the most difficult fish for many aquarists to maintain. They are extremely sensitive to water parameters and water quality, and prone to develop skin parasites if not maintained in very stable and acceptable water. I have previously maintained these fish and can vouch for the parasite problem. I also have them now, both the Sphaerichthys osphromenoides osphromenoides species (the original or common chocolate gourami) and the much rarer Sphaerichthys osphromenoides selatanensis that closely resembles the former. These are definitely not fish for beginning aquarists. Aside from the very important considerations over water, there are limited options for suitable tankmates.
A group of 8 cardinal tetras would be fine, and a group of 3-5 corydoras like pandas would be good. Corydoras, like the tetras and all characins, are shoaling fish that prefer to be (and live healthier lives) in groups, minimum 3 for corys but preferably more. Tetras should be in groups of six minimum, or more if space permits. Which brings me to the Bloodfins, good companions for cardinals and corys but in a group of 5-6. Barbs are the same re groups, but adding them with the others in this tank is getting crowded and I wouldn't.
Don't forget the tank has to cycle once the fish are in it; you mention having two large plants, that is a good start. I would also get a small bottle of Seachem's Stability, it is a biological supplement that is live bacteria to "seed" the tank. This plus the plants should handle the ammonia and nitrite from the first fish, but only put a few fish in at first; maybe the 5-6 bloodfins on their own. After a few days, add the cardinals (or the pandas), then a few days later the pandas (or the cardinals). This allows the bacteria time to multiply to handle the increased ammonia, even though the plants--if healthy and growing--will do most of this. Be regular in your weekly partial water change of 25-35%, and you will have a very beautiful and healthy aquarium.