I would not use Paypal to build credit. I am not even sure they report to credit agencies.
In about 2005 my credit was not great. I had made a few mistakes in the past but had no credit cards, very little debt and had been using my bank account debit cards for years.
So I decided to get a couple credit cards to improve my credit. I had a paypal account since they started in the 1990s so I applied for their Visa card. Paypal accepted my application and gave me a card with a credit limit of $1000 which was too low to be useful. At the same time I applied with Capital One and they gave me a card earning 2% miles with a credit limit of $12,000 but with an annual fee after the first year.
I used both for over a year. Always paid them off every month before any interest was due. So I asked for a credit line increase from both companies. Paypal declined, Capital One raised me to $20,000. I canceled the Paypal card and have been using the Capital One card ever since. Never paid interest on it but now pay an annual fee of $100. The upside is that I improved my credit score, I build travel credits and get back a few thousand dollars a year in paid travel expenses (they rebate travel expenses). They also have cash back cards but the travel works better for me.
And now my credit score is high enough to get those 0% or really low interest loans on new cars.