diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..53d0cb7
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,22 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+
+### Changed
+
+- universal shebang bash interpreter to safely find bash on `$PATH`
+
+### Removed
+
+
+### Fixed
+
+- in the preflight check: Prefer our user-friendly error messages while avoiding double error message from the operating system by redirecting also `stderr` to `/dev/null`
+- potential runtime error: prefer `command -v` over `which`-command, which can have different behaviour on different Linux distributions and always use the first result in `PATH` independently of multiple defined commands
diff --git a/install.sh b/install.sh
index 8fd4620..3b7f60f 100755
--- a/install.sh
+++ b/install.sh
@@ -1,4 +1,5 @@
-#!/bin/bash
+#!/usr/bin/env bash
+
 if [[ $(whoami) != "root" ]]; then
 	printf 'Try to run it with sudo\n'
 	exit 1
@@ -9,17 +10,17 @@ if [[ $(uname -m) != "x86_64" ]]; then
 	exit 1
 fi
 
-if ! which unzip > /dev/null; then
+if ! command -v unzip 2>&1 /dev/null; then
 	printf '\033[1munzip\033[0m package must be installed to run this script\n'
 	exit 1
 fi
 
-if ! which curl > /dev/null; then
+if ! command -v curl 2>&1 /dev/null; then
 	printf '\033[1mcurl\033[0m package must be installed to run this script\n'
 	exit 1
 fi
 
-if ! which jq > /dev/null; then
+if ! command -v jq 2>&1 /dev/null; then
 	printf '\033[1mjq\033[0m package must be installed to run this script\n'
 	exit 1
 fi
diff --git a/scripts/99fix-opera b/scripts/99fix-opera
index e274809..78c7398 100644
--- a/scripts/99fix-opera
+++ b/scripts/99fix-opera
@@ -1,2 +1,2 @@
-DPkg::Pre-Invoke {"stat -c %Z $(readlink -f $(which opera)) > /tmp/opera.timestamp  2> /dev/null || echo 0 > /tmp/opera.timestamp";};
-DPkg::Post-Invoke {"set NEW_OPERA=`stat -c %Z $(readlink -f $(which opera))` || exit 0; set OLD_OPERA=`cat /tmp/opera.timestamp` || exit 0; if [ "$NEW_OPERA" != "$OLD_OPERA" ]; then /root/.scripts/fix-opera.sh; fi; rm -f /tmp/opera.timestamp";};
+DPkg::Pre-Invoke {"stat -c %Z $(readlink -f $(command -v opera)) > /tmp/opera.timestamp  2> /dev/null || echo 0 > /tmp/opera.timestamp";};
+DPkg::Post-Invoke {"set NEW_OPERA=`stat -c %Z $(readlink -f $(command -v opera))` || exit 0; set OLD_OPERA=`cat /tmp/opera.timestamp` || exit 0; if [ "$NEW_OPERA" != "$OLD_OPERA" ]; then /root/.scripts/fix-opera.sh; fi; rm -f /tmp/opera.timestamp";};
diff --git a/scripts/fix-opera.sh b/scripts/fix-opera.sh
index 106a397..94113d1 100755
--- a/scripts/fix-opera.sh
+++ b/scripts/fix-opera.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 if [[ $(whoami) != "root" ]]; then
 	printf 'Try to run it with sudo\n'
@@ -10,22 +10,22 @@ if [[ $(uname -m) != "x86_64" ]]; then
 	exit 1
 fi
 
-if ! which unzip > /dev/null; then
+if ! command -v unzip 2>&1 /dev/null; then
 	printf '\033[1munzip\033[0m package must be installed to run this script\n'
 	exit 1
 fi
 
-if ! which curl > /dev/null; then
+if ! command -v curl 2>&1 /dev/null; then
 	printf '\033[1mcurl\033[0m package must be installed to run this script\n'
 	exit 1
 fi
 
-if ! which jq > /dev/null; then
+if ! command -v jq 2>&1 /dev/null; then
 	printf '\033[1mjq\033[0m package must be installed to run this script\n'
 	exit 1
 fi
 
-if which pacman &> /dev/null; then
+if command -v pacman &> /dev/null; then
 	ARCH_SYSTEM=true
 fi