Re: which city has best football training clubs for kids and beginners ?
If it's really a football career you're looking into, then you should know that FC Basel are the most dominant team in the country. FC Zurich and Young Boys (Bern) probably also have good infrastructure.
To be honest, Switzerland isn't really a country for a footballing career. What could be interesting, if you have the right level and skills (and some luck, because you always need luck in this career and in general for most careers), is to eventually move to France or Germany where football is much bigger.