Non-EU countries make trade deals with the EU who is collectively acting on their member states behalf.
There will _NEVER_ be a "side" trade deal between Britain and an EU member state directly.
Don't feel too bad about not knowing this. The original Minister for Brexit David Davis (& embarrassingly enough a former Europe minister) also didn't know this.
https://www.independent.co.uk/news/uk/politics/minister-for-...
> However one of the main basic features of the European Union is that EU countries cannot negotiate individual trade deals without side countries and instead do so as a bloc of 28.