Registration Certificate for EU Citizen in Portugal

I am Croatian that came to Portugal and I'm trying to find a job here.
I came here at the end of December so in less than a month my 3 months of staying here without reporting my presence are expiring.
I applied to jobs and I am in interview process for few companies but because of current situation with Covid-19 I am worried my 3 months (before 90 days to apply for Registration Certificate) will expire before I sign a job I am wondering what are considered sufficient resources and which way to proof this in case I need to apply by declaration under oath that I have enough financial resources to support myself?
I'm hoping I don't need to return in Croatia now.
Thank you!

Hello Ivana.
I had friends that needed to return to Brazil for same reason.
It's very sad, I hope you well.
When I was about to attempt to extend my partner's Visa SEF told my lawyer they were looking for evidence that expiry date on 3 month visa would not expire (She was here first 3 months but the 90 days within 180 has a six month period stated on visa), that we had €5000 (maybe €2500 each?) in bank . Maybe they may be flexible on that.
Also that she had ample insurance for health.
They did not ask for proof of accomodation paid for which I found strange, as that is a big part of expense.

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