diff --git a/ptbposter/ptbposter-new-engines.clo b/ptbposter/ptbposter-new-engines.clo
index 333463a43b086e0b3c4b26d5f7ead1189687f2c2..1efbe05d209672716b89abe3c7ab55afce21a999 100644
--- a/ptbposter/ptbposter-new-engines.clo
+++ b/ptbposter/ptbposter-new-engines.clo
@@ -12,6 +12,7 @@
 }{}
 
 \RequirePackage[no-math]{fontspec}
+\RequirePackage[mathit=sym]{unicode-math} 
 
 \ifSERIF
   \setmainfont{texgyrepagella}[
@@ -22,32 +23,43 @@
     ItalicFont=*-italic,
     BoldItalicFont=*-bolditalic]
 \else
-  \setmainfont{texgyreheros}[
+  \setsansfont{texgyreheros}[
     Ligatures=TeX,
     Extension=.otf,
     UprightFont=*-regular,
     BoldFont=*-bold,
     ItalicFont=*-italic,
     BoldItalicFont=*-bolditalic]
+  \setromanfont{texgyreheros}[
+    Ligatures=TeX,
+    Extension=.otf,
+    UprightFont=*-regular,
+    BoldFont=*-bold,
+    ItalicFont=*-italic,
+    BoldItalicFont=*-bolditalic]
+  \renewcommand*\familydefault{\sfdefault}%
 \fi  
 
-\renewcommand*\familydefault{\sfdefault}%
-
 \ifMATHSERIF 
-  \RequirePackage{unicode-math}
   \setmathfont{texgyrepagella-math.otf}[
     math-style=TeX,
     bold-style=TeX,
   ]
 \else
-  \iftrue
-    \usepackage[usefilenames,weight=Regular]{firamath-otf}
-    \setoperatorfont\mathsf 
-    \unimathsetup{partial=upright}%
-    \RequirePackage{mathastext}  
-  \else
-    \usepackage{newtxsf}% XeTeX crashed
-  \fi
+  \setmathfont{FiraMath-Regular.otf}[
+    Scale=1,
+    math-style=TeX,
+    bold-style=TeX,
+    Numbers={Lining,Proportional},
+  ]
+  %\RequirePackage[usefilenames,weight=Regular]{firamath-otf}
+  \setoperatorfont\mathsf 
+  \unimathsetup{partial=upright}% 
+  %\RequirePackage{mathastext}% nicht so gut
+  \setmathfont{texgyreheros-regular.otf}[range=up/{Latin,Greek,num}]
+  \setmathfont{texgyreheros-italic.otf}[range=it/{latin,greek}]
+  \setmathfont{texgyreheros-bolditalic.otf}[range=bfit/{latin,greek}]
+  \setmathfont{texgyreheros-bold.otf}[range=bfup/{latin,greek}] 
 \fi
 
 \setmonofont{AnonymousPro-Regular}[%
diff --git a/ptbposter/ptbposter.cls b/ptbposter/ptbposter.cls
index c29b1fa5ffbab4b67e332e4fdf3ae4959eeb9d53..8508378a54897448ef48b24a3c3cd2e7656d4c0d 100644
--- a/ptbposter/ptbposter.cls
+++ b/ptbposter/ptbposter.cls
@@ -330,7 +330,7 @@
   \PTBlandscapetrue
 \fi
 
-\RequirePackage{relsize}\renewcommand\RSpercentTolerance{0}
+\RequirePackage{relsize}\renewcommand\RSpercentTolerance{0}% ???
 
 \newcommand*\scaleFontSizes[1]{%
   \global\PTB@default@fsize=#1\PTB@default@fontsize@base