Your account is currently on the Hobby plan with a trial credit balance of $3.47 remaining from the one-time $5 trial grant. Once the trial period ends (30 days or when credits run out), the Hobby plan costs $5/month, not $1, and that $5 subscription fee includes $5 of resource usage credit. You can review full pricing details at railway.com/pricing.

And why does it say here after the trial period, the next one will be $1? "Start with a 30-day free trial with $5 credits, then $1 per month"

The $1 is referring to the credits that is included in the free plan if you downgrade to the free plan after your trial. As mentioned above, you are not on the free plan, but instead on the upgraded hobby plan.

And how to switch to this tariff? Won't he fit mine?

If I am remember it correctly, the only way to switch to the free plan in your case is to cancel your hobby plan and downgrade to the free plan in the next billing cycle where you are no longer on any plan.