There's nothing in my contract about a minimum time staying here,
there's nothing that says verbal agreements are binding. However, I
feel like cheating and being a loss of time for the company, but it
looks like leaving now is better than after a project has started. The
company, however, has a good salary and has given me lots of freedom
for doing some technical choices, so I'd prefer to keep the bridges
Verbal agreements are not worth the paper they are written on. And—in an extreme case—they hurt you in the end because the company will ultimately have more resources at hand to perhaps legally challenge you in a confrontation about it than you have to counter such a claim.
But you also say this:
During the last 2 weeks I've been offered 2 other jobs, and I've found
some offers myself that look perfect for me. It's really tempting, but
I feel something's wrong if I start looking at other jobs.
A company is not a person & a job is not a life. Even if your current employer would be upset by you leaving, if you do it right nobody gets upset & no bridges are burned. More importantly: You should not treat an employer/employee relationship strictly as if it’s some deep personal relationship in which one would get upset at the there by leaving.
At the end of that day even a “career” is still a “job.” And your task for yourself is to further your career in a way that benefits others but—most importantly—works best for yourself.
Meaning, based on what you have described, I would weigh the benefits of other positions. Most likely accept one of those positions. But do so in a way that reflects your current employer.
How to balance that? Who knows. In the U.S. 2 weeks notice is standard & in some cases giving more than 2 weeks notice is a good way of ensuring bridges are not burnt. But perhaps the best way to state this is to negotiate with the future employer and state, “I’m going to give my current employer 2 weeks notice, but there might be some desire from them to allow me to consult. Is that something we can work out?”
Then on the current employer front, approach them, tell them you accepted a new position & give standard 2 weeks notice. But also state, “I understand that you have other projects you would want me involved in, but nothing has happened so far. That is why I am leaving. Do you still want to keep in touch regarding the future project to see if there is any way we can work together on a limited basis?”
What it all boils down to is you cannot be strung along by verbal agreements. And at the end of the day, folks on your current employer’s side will be upset. But in the great scheme of things, you might look back on this gig and be upset you didn’t do what is best for you.
Like I said at the outset a company is not a person & a job is not a life. Do what is best for your career & do it in a way that respects others. All should be good.