Hi Lotta😊
It should be safe to use together with your Eucerin Anti-Pigment series.
GF Solution contains growth factors and peptides — no acids or strong exfoliants — so it does not affect or interfere with the action of thiamidol. Thiamidol works to reduce pigmentation by inhibiting tyrosinase, an enzyme in pigment production, and is not negatively affected by peptides or growth factors.
So there are no known negative interactions between growth factors and thiamidol. However, always do a small patch test to see how your skin reacts.
Avoid using it with acids or direct vitamin C in the same routine to protect the effectiveness of the peptides.
I hope my answer can be helpful and that you have a lovely Friday🌞