My personal configuration for a fresh Mathematica installation. Run it step by step in case our preferences differ.

Preferences.m

(* ::Package:: *)

(* ::Section:: *)
(*Preferences*)


CurrentValue[$FrontEnd,"NotebooksMenuHistoryLength"]=25


(* ::Subsection:: *)
(*Events*)


SetOptions[
  $FrontEnd
, NotebookEventActions :> {
    {"MenuCommand", "New"} :> CreateNotebook["Default"]
  } (* to create a notebook with a fixed size instead of inheritting size from the current one. *)
]


(* ::Subsection:: *)
(*Notebook Interface*)


CurrentValue[$FrontEnd, {TranslationOptions,"Enabled"}] = False;   


CurrentValue[$FrontEnd, Language] ="English"; 


If[ 
  $VersionNumber >= 11.3
, CurrentValue[$FrontEnd, {StyleHints, "GroupOpener"}] = "OutsideFrame"
, CurrentValue[$FrontEnd, ShowGroupOpener] = True
];


CurrentValue[$FrontEnd, ShowPredictiveInterface] = False;


CurrentValue[$FrontEnd, ShowAutoSpellCheck] = False;


CurrentValue[$FrontEnd, {CodeAssistOptions, "AutoConvertEnable"}]=False;


(* ::Text:: *)
(*- Enable blinking cell insertion point -> False*)


(*the main reason is the make comments pink and strings orange*)

SetOptions[$FrontEnd
, AutoStyleOptions->{
    "CommentStyle"->{
      FontColor -> RGBColor[1., 0., 1.]
    , ShowAutoStyles -> False
    , ShowSyntaxStyles -> False
    , AutoNumberFormatting -> False
    , TranslationOptions -> {"Enabled" -> False}
    , FontWeight -> "Normal"
    }
  , "StringStyle"->{
      FontColor -> RGBColor[1., 0.5019607843137255, 0.25098039215686274`]
    , ShowAutoStyles -> False
    , ShowSyntaxStyles -> False
    , AutoNumberFormatting -> False
    , TranslationOptions -> {"Enabled" -> False}
    }
  }
]


(* ::Subsection:: *)
(*Messages*)


SetOptions[$FrontEnd,MessageOptions->{
  "AllowDisablingWarnings"           -> True
, "CodeCaptionWarning"               -> True
, "CompatibilityToolWarning"         -> True
, "ConsoleMessageAction"             -> "PrintToConsole"
, "ErrorAction"                      -> "PrintToConsole"
, "ExplainBeepHelp"                  -> False
, "IgnoreTagBoxDeletionWarning"      -> True
, "InsufficientVersionWarning"       -> True
, "KernelMessageAction"              -> "PrintToConsole"
, "MathMLPasteWarning"               -> True
, "MaxMessageCount"                  -> 3
, "MessageCountResetTime"            -> "2.`"
, "TeXPasteWarning"                  -> True
, "TraditionalFormEvaluationWarning" -> True
, "UseVersionedStylesheetWarning"    -> True
, "WarningAction"                    -> "Beep"
}]


CurrentValue[$FrontEnd, PrintAction] = "PrintToConsole"


(* ::Section:: *)
(*System Settings*)


$HistoryLength = 0


SetOptions[
  $FrontEnd
, NotebookSecurityOptions->{"TrustByDefault"->True,"UntrustedPath"->{}}
]


(* ::Section:: *)
(*Packages*)


Get@"http://www.mertig.com/shortcuts.m"


(* ::Text:: *)
(*after installing, go to Ctrl+Shift+J and add SelectionMove[SelectedNotebook[], All,Cell], save and done.*)
(*Now Ctrl+t selects current cell.*)


<<Shortcuts`


<<GeneralUtilities`


Import["https://raw.githubusercontent.com/kubapod/mpm/master/install.m"]


Needs @ "MPM`"


MPM`MPMInstall["kubapod", "devtools"]


Needs@"DevTools`"


CodeTemplatesEnable[];
NotebookActionsEnable[];


CurrentValue[
    $FrontEnd, "DefaultPackageStyleDefinitions"
] = FrontEnd`FileName[{"DevTools", "DevPackageDark.nb"}]


(* ::Section:: *)
(*Autoload / init.m*)


FilePrint@FindFile @ "init.m"


PutAppend[
  Unevaluated @ Needs["GeneralUtilities`"]
, FindFile @ "init.m"
]


(* ::Section:: *)
(*LinkSnooper*)


EvaluatorNames->{
 "Local" -> {"AutoStartOnLaunch" -> True}, 
  "LinkSnooper" -> {
   "AutoStartOnLaunch" -> False, "MLOpenArguments" -> 
    "-LinkMode Launch -LinkName {oq}`javaw` -classpath {iq}`jlinkjar`{iq} \
com.wolfram.jlink.util.LinkSnooper -noinit -kernelname \
{iq}`mathkernel`{iq}{oq}"}}


(* ::Section:: *)
(*IDE*)


(* ::Text:: *)
(*Go get IntelliJ IDEA community edition and go to http://wlplugin.halirutan.de/index.php/downloads to learn how to install Halirutans plugin*)
(**)
(*rigth click on .nb file and associate file type with external editor.*)