From now on?
That's pretty bad buildup (and/or rust). Car was neglected/abused. It's like "animal cruelty", but for technical objects, machines etc.
Regular maintenance (religiously) should be done long time ago (for last 100000 km). Now it's too late.
You can clean it a bit with rag + paint remover (maybe gel type) or some other strong/heavy solvent. No abrasives!
Plus engine flush every oil change (once a year or 10000 km max.).
Or full disassembly (head gasket job) if you want it perfect.