ClearAll[f];
R1=20;
R2=3;
U1=230;
Pp=5;
ω=314;
X1=8;
X2=15;
R22=3*R2;
R23=10*R2;

Plot[{((3*R2*(U1^2)*Pp)/(ω-Ω*Pp))*(1/((((R1+(R2/((ω-Ω*Pp)/ω))))^2)+(((X1+X2))^2))),((3*R22*(U1^2)*Pp)/(ω-Ω*Pp))*(1/((((R1+(R22/((ω-Ω*Pp)/ω))))^2)+(((X1+X2))^2))),((3*R23*(U1^2)*Pp)/(((ω-Ω*Pp)/ω)*ω))*(1/((((R1+(R23/((ω-Ω*Pp)/ω))))^2)+(((X1+X2))^2)))},{Ω,0,62.8},Axes->True,AxesLabel->{"->Ω[\!\(\*SuperscriptBox[\(rad∙s\), \(-1\)]\)]","↑M[Nm]"},LabelStyle->Directive[Black,Bold]]

ClearAll[f];

f[x_]:=Piecewise[{{1-(E^(-(x/6))),0≤x≤9},{(E^(-((x-9)/6)))*(1-(E^(-(9/6)))),9.05≤x<25}}]
Plot[f[x],{x,0,25},PlotStyle->{Blue,Thick},AxesLabel->{"t[s] ->","Δϑ"},LabelStyle->Directive[Black,Bold]];
Plot[1-(E^(-(x/6))),{x,9.05,25},PlotStyle->{Thick,Red}];
Show[Plot[1-(E^(-(x/6))),{x,0,25},PlotStyle->{Thick,Red}],Plot[1-(E^(-(x/6))),{x,0,11.36},PlotStyle->{Thick,Blue},AxesLabel->{"t[s] ->","Δϑ ΔM"},LabelStyle->Directive[Black,Bold]],Plot[f[x],{x,0,25},PlotStyle->{Blue,Thick}] ,Plot[0.85,{x,0,25},PlotStyle->{Thin,Black,Dashed}]]