People can believe what they want to but mathematics of this basic kind is pretty resilient to opinions.
https://fullfact.org/europe/uk-eu-trade/
As an added kicker a bunch of those UK exports rely on producing finished goods from materials supplied via the EU.
A trade deficit or otherwise is a hugely over-simplistic assessment of the situation and is, quite simply, misleading. Something that does significant harm to our goods trading relationship with the European Union will have a considerable effect on domestic consumption.
As the terms of negotiations and the current points stand there is no way an agreement is possible.
The big reaasons for this are May's entirely unnecessary speech at the Tory Party conference drawing up a bunch of red lines to appease the UKIPpers and entirely robbing her of flexibility and how the EU negotiates: a slow, consensus based process.
The Conservative actions at and around their conference were a massive mistake.
To be honest, if the plan is to crash out with no deal, blame the EU and try and win an election on the bulldog spirit of resisting those who wanted to pick on the UK what's going on fits that pattern almost perfectly. I'm going to go with incompetence and someone eating a law book to provide legal basis for why the UK shouldn't pay any obligations agreed during EU membership after it.
This is not legally unsound. There is simply no body that can force the UK to pay the commitments it agreed as part of the EU once we've left and that's the point the UK have been making, the payment demands are not enforceable. It is, however, perhaps morally unsound and gives a moment of pause to any nation we're looking for a trade deal from. Why deal with a country that refuses to pay its commitments because there's no viable legal way of compelling them to do so? Requires a high level of supervision of such an agreement. Something that in the current bizarre context would be seen as a violation of sovereignty, having a 3rd party group that can tell us what to do.