It’s most important you appoint an independent solicitor and that you do not, under any circumstances, use the solicitor recommended by either the developer or estate agent.
Just like in the UK get quotes and see what’s included and not included ie powers of attorney, applying for NIE numbers, attendance at notary etc, setting up utilities, rates/IBI, also will the solicitor charge you extra if there is a mortgage deed etc
Email the solicitors on this site for a quote – some are even dual qualified (ie English & Spanish). But ignore the usual 1% plus VAT, although if apartment is low price there will be minimal fees etc. High value apartments can be done on an hourly rate with capped fees etc. Everything is negotiable.