I used to know someone who was completely bilingual in English and Spanish. It struck me when they were on the phone while also talking with someone in the room. They were hearing Spanish in one ear and English in the other ear and that wasn't a problem at all. They were switching back and forth between speaking Spanish on the phone, with what sounded like a Spanish accent to me, and speaking English to a person in the room, with an English accent that sounded like a neutral probably mostly southeastern English accent to me. Also not a problem.
I spent 5 years scraping together enough understanding of French and classical Latin to be able to read rather slowly in those languages and be possibly just about understandable when speaking French badly and slowly because I was thinking in English and translating into French. I'm impressed by people who are even passably competent in 2 or more languages.
I went to France a fair few years ago for a few weeks. In general, my experience was that most French people would have a decent try at understanding me. The impression I got was that most of them were probably thinking along the lines of "It's nice that he's trying, but what the hell is he saying?" Quite often, there would be someone around whose English was a lot better than my French.
On a tangent, language is what started me watching Game of Thrones. I was reading an article on conlangs and there was a clip from GoT as an illustration. It looked cliched - half naked barbarian warlord and civilised lady, blah blah blah. I knew nothing about the characters, plot, backstory...nothing at all about any of it. The dialogue was wholly in Dothraki. Not even subtitled. What struck me was that the actor playing the barbarian warlord was speaking Dothraki fluently, casually and with an accent that fitted the language. They gave every impression of someone for whom Dothraki was their native language, the language they learned as an infant, spoke all the time and thought in. The actor playing the civilised lady was speaking Dothraki pretty much fluently, but not casually. There were slight pauses, particularly at the beginning of sentences. Their accent didn't fit the language. They gave every impression of someone for whom Dothraki was a foreign language they'd learned recently and that they were thinking in another language and translating it into Dothraki before speaking. I thought it was a fine example of acting.
pretty much at the tip of a hat if he's talking to another Geordie (when our newest neighbour moved in it was like they were speaking a different language at times). He apparently spent several years learning to lose his accent as a teen and young adult to improve his ability to get jobs down here where no one has an accent (everyone from anywhere lese does though).
