nostalgisch
nostalgic
Feeling or expressing a longing, often idealized and sentimental attitude toward the past.
Beim Anblick der alten Fotos wurde er ganz nostalgisch.
At the sight of the old photos, he became very nostalgic.

nostalgic
Loading your saved state.
nostalgic
Feeling or expressing a longing, often idealized and sentimental attitude toward the past.
Beim Anblick der alten Fotos wurde er ganz nostalgisch.
At the sight of the old photos, he became very nostalgic.

The adjective 'nostalgisch' (nostalgic) belongs to the noun 'die Nostalgie' (nostalgia). If you know the noun, you can easily derive the meaning of the adjective.
Er spürte eine Welle der Nostalgie, als er seine alte Schule besuchte.
He felt a wave of nostalgia when he visited his old school.
'Nostalgisch' (nostalgic) is often used with the verb 'werden' (to become) to describe the beginning of the feeling. It can also stand as an attribute before a noun to describe something that triggers this feeling.
Jedes Mal, wenn ich dieses Lied höre, werde ich ein bisschen nostalgisch.
Every time I hear this song, I become a little nostalgic.
The trigger for the nostalgic feeling is often introduced with prepositions such as 'bei' (at/when) or 'durch' (through/by). Typical formulations are 'beim Anblick von...' (at the sight of...) or 'beim Hören von...' (when listening to...).
Beim Betrachten der alten Familienalben wurde die Großmutter ganz nostalgisch.
While looking at the old family albums, the grandmother became very nostalgic.
retro
'retro' and 'nostalgisch' both have to do with the past, but they do not mean the same thing. 'retro' mainly describes a visible style, for example in clothing, furniture, or music. 'nostalgisch' describes more of a feeling: you think back to earlier times fondly or with longing. An object can look retro and thereby awaken nostalgic feelings. The words can be confused because they often occur together. 'retro' fits the style, while 'nostalgisch' fits the mood or memory.

Beim alten Familienfoto wird Mehmet plötzlich nostalgisch.
When Mehmet looks at the old family photo, he suddenly becomes nostalgic.
Beim Einkaufen entdeckt Lena eine Lampe im Retro-Design.
While shopping, Lena discovers a lamp with a retro design.