Do I need transit visa for Amsterdam Airport? [duplicate]

If you are travelling on a single ticket, then no, you shouldn't need a transit visa.

While I have doubt about the general situation of a Palestinian with a Lebanese travel document:

• The official site tells us that "You only need an airport transit visa if your nationality appears on the list of countries whose nationals require a visa (PDF, 69 KB)" and the list does neither contain Palestine nor Lebanon,
• Multiple third-party web sites tell us that "Holders of a travel document for Palestinian stateless/refugees which has been issued by Egypt, Lebanon or Syria need an airport transit visa ((A 1951 Convention travel document/ A 1954 Convention travel document)."

there is an exemption that is the same on all sites and applies to you:

If your nationality appears on this list, check whether you have an exemption. An airport transit visa is also not required if you: ... have a visa or residence permit for a country in the Schengen Area, the EU or the EEA

Since Bulgaria is part of the EU, your Bulgarian visa should suffice.