only a few questions

what i the maximum of gold you can have ? ( and does a bank exist ?)
is the change to get a shiny on all the same ? is it harder to catch them ? do they have a stats bonus ?
is it possible to catch all pokemons without trading ? which pokemons do i need to trade if they are not available ?
can i trade between 2 savefiles from myself ? or fight ?

I don't know about the max gold thing, but it's likely to be $999999.
Chance of a shiny is 1/8192 for all pokemon and there currently is no way to increase those odds nor do they receive a stat bonus.
You should be able to catch all pokemon except for the two fossil pokemon. You will have to trade to get the fossil that you don't select.
Since both of your savefiles use the same online ID you cannot trade or fight yourself.

All of those answers are correct, also the only Pokemon that you will need to trade in order to get are the starters (besides the one that you picked), the fossils, and you need to trade in order to evolve Linkite. In addition, there are several Pokemon that are currently unavailable, including Shrimputy, Lavent, Antarki, Hazma and most of the legendaries.

Wait but I saw someone on this wiki with a team in their Signature that included a Krillvolver? Or do you think that was just wishful thinking?

I think it's just plans for the future, Krillvolver is currently not catchable.

For instance, my dream team includes Laissure, who isn't in Beta 4 either:

Ah OK thanks, I spent ages looking for a past event or something where he could have gotten it xD
Also, laissure and the electric/flying looking awesome,nice work on those sprites

Also, there is actually a method to increade the rate of shinies obatined through eggs. The Masuda method is in the game.

So are the pokemon that you put in the mystery gift technically pokemon from another country (since I live in the U.S.) and they say OT JV? Or do they not actually come from you and are therefore not foreign?

i got another question .... how work the friendship here ?

Pretty sure it works like normal - each pokemon has a base stat that you can increase by walking 250-odd steps, levelling up or by massaging your Pokémon.

where can i do such a massage ?

Bealbeach Casino will massage once a day

so it will take some more days to get all pokemons evolved ^^ ok thank you

No worries and yeah should take a while - bear in mind that it will also lose friendliness if it faints.

yeah ..... do you know with how much friendship they start if i catch them without this luxery ball and how much the massage give ?

Also using items like rare candies, vitamins, potions etc. raises happiness I believe. So does giving it a held item (I'm pretty sure the Soothe Bell is in the game? that doubles happiness gains)

The luxury ball and soothe bell make it so that any gain in happiness is boosted by one point - the massages give different amounts based on the happiness level, (it gets harder the higher you go) and there are also berries that work, but they lower EVs in a stat.

The amount of friendship a pokemon starts with can be found on the wiki. I think it's typically 70. If the massage is based off the massage in the original games, there is a 6% chance to +30, a 20% chance to +10, and a 74% chance to +5.

I have a question always when i cath a Magikarb my game says an error what can i do?

https://pokemonuranium.forumeiro.com/t1006-error-after-fish-catching-fortog
That would be this error. Read what Twitch said.
For future reference, questions about errors belong in the Help Desk section, where you can check out the sticky thread for known errors as well as what other people have posted about.