How make second validation in request class - request

Question

i make form and this request go to controller store:
public function store(StoreTermRequest $request): RedirectResponse
{
$this->authorize('terms.create');
$request->addTerms();
return redirect(route('terms'));
}
rules of request:
public function rules()
{
return [
'start_date' => ['required', 'date'],
'end_date' => ['required', 'after_or_equal:start_date', 'date'],
'start_day' => ['required', 'date_format:H:i'],
'end_day' => ['required', 'after_or_equal:start_day', 'date_format:H:i'],
'start_break' => ['required', 'date_format:H:i'],
'end_break' => ['required', 'after_or_equal:start_break', 'date_format:H:i'],
'time_one_visit' => ['required', 'integer', 'min:1'],
'work_days' => ['present', 'required'],
'work_days.*' => ['present', 'required', new Enum(Days::class)],
'doctor' => [
'required', 'exists:doctors,id', 'integer',
],
];
}
then i make buisness logic, from generate date to single visits terms then i want check whether the given dates are free. that's why i want make second validation
public function addTerms()
{
$startDayInMonth = strtotime($this->start_date);
$endDayInMonth = strtotime($this->end_date);
$startDayOfHour = strtotime($this->start_day);
$endDayOfHour = strtotime($this->end_day);
$startBreak = strtotime($this->start_break);
$endBreak = strtotime($this->end_break);
$workingDays = $this->work_days;
$timeOneVisit = $this->time_one_visit * 60;
$doctor = $this->doctor;
$doctorBefore = [];
$dateVisitBefore = [];
$startVisitBefore = [];
$endVisitBefore = [];
$j = $startDayInMonth;
while ($endDayInMonth >= $j) {
if (!in_array(date('N', $j), $workingDays)) {
$j += 86400;
continue;
}
$j += 86400;
$i = $startDayOfHour;
while ($endDayOfHour > $i) {
if ($startBreak <= $i && $endBreak > $i) {
$i = $endBreak;
}
$validator = Validator::make(
[
'start_visit' => date('H:i', $i),
'end_visit' => date('H:i', $i + $timeOneVisit)
],
[
'start_visit' => [new FreeTerm()],
'end_visit' => [new FreeTerm()],
]
);
if ($validator->fails()) {
//
}
array_push($doctorBefore, $doctor);
array_push($dateVisitBefore, date('Y-m-d', $j));
array_push($startVisitBefore, date('H:i', $i));
array_push($endVisitBefore, date('H:i', $i + $timeOneVisit));
$i += $timeOneVisit;
}
}
for ($i = 0; $i < count($doctorBefore); $i++) {
DB::table('terms')->insert([
'doctor_id' => $doctorBefore[$i],
'date_visit' => $dateVisitBefore[$i],
'start_visit' => $startVisitBefore[$i],
'end_visit' => $endVisitBefore[$i]
]);
}
}
and its successful validation but what write here to return to form after fail with error message
if ($validator->fails()) {
//
}
i tried
return redirect()->to(route('terms.create'));
return back()->withErrors($validate->errors()->withinput();
and a lot of combinations around this in controller in request class, but i'm done.
i want to see clear answer because my english is not perfect :P