Sinkov, that is nonsense.

Like I said, trading within the EU is as easy as trading with a UK company.

The EU has also brokered many very good trade deals outside the EU which we benefit from.

The main drawback with trading outside the EU is location. If you look at the map you will see that Australia, USA, China etc are a long way away. Normal transit times are 6-8 weeks for these areas.

If we strike a deal with, say, a company in Australia then we would have to stump the money up front and wait 8 weeks before we get the goods. We are then vulnerable to exchange rate fluctuations (a run on the pound may mean that the deal is not worth doing).
If, as is often the case, there is a problem with the goods when we receive them, it is a much harder job to rectify it.
And the reverse is true if we are selling goods.

Dealing with Germany for example means that we stump the money up front and we receive the shipment usually within two days, no tariffs, no border checks, no import duty etc. Returning faulty goods is a simple process.

BUT...we STILL deal with non EU companies despite this.

When we leave the EU then, depending on the deal, we will certainly lose some of our trading partners. A Hungarian company could do similar trade with a Dutch company as they used to do with us without the hassle. And I know for a fact that these countries are currently making their plans for when we leave the EU.

We are about to leave a very successful free trade block for no good reason.

Politicians (who generally have no idea about how trade actually works) are telling us it will be easy to replace this lost trade by trading outside the EU. Boris recently said "f**k trade".
Perhaps we will magically get better trade deals with these countries than we have at present.
Why should that be? The EU has brokered many good trade deals because of the size of the EU. why should the UK (much smaller) get a better deal?
We will see, but whatever the deal, these countries are still going to be much further away that mainland Europe - and that is a real barrier to trade.

On top of that, these countries have different trading standards. EU law on this means that our imports (and exports) have to be of a good standard of quality and safety. Are we happy to import american chlorinated chicken or Chinese fireworks for instance?