You don't pay 30 euros (or however much) to bid on a job. You have a certain amount of Connects per month and you "spend" one or two of them each time you submit a proposal for a job. But those Connects are free. You don't spend anything in advance unless you have a paid membership, which many people don't have. (I don't.)
Oherwise, you're not charged any fees until you complete a job/complete a week of hourly rate work. And those are a percentage of the job.
You should read through these articles to try to get a better understanding. https://support.upwork.com/hc/en-us/sections/360002707333-Send-Proposals
Otherwise, you are likely to fall for a scam. Definitely never pay to find work using Upwork.