ReadFileFromDisk kernelmode - c++

Question

I want to read a file from disk using a kernelmode driver. When I try to convert the char buffer to a PCWSTR it either returns "/" or ???????? or some other random characters. I took https://support.microsoft.com/de-at/help/891805/how-to-open-a-file-from-a-kernel-mode-device-driver-and-how-to-read-fr as reference.
I tried the following:
void ZwReadFromFile(PCWSTR FileName, char* outStr)
{
UNICODE_STRING UnicodeName;
OBJECT_ATTRIBUTES ObjectAttribute;
HANDLE FileHandle;
NTSTATUS NTStatus;
IO_STATUS_BLOCK IOStatusBlock;
char FileBuffer[BUFFER_SIZE];
LARGE_INTEGER ByteOffset;
RtlInitUnicodeString(&UnicodeName, FileName);
InitializeObjectAttributes(&ObjectAttribute, &UnicodeName,
OBJ_CASE_INSENSITIVE | OBJ_KERNEL_HANDLE,
NULL, NULL);
NTStatus = ZwCreateFile(&FileHandle,
GENERIC_READ,
&ObjectAttribute, &IOStatusBlock,
NULL,
FILE_ATTRIBUTE_NORMAL,
0,
FILE_OPEN,
FILE_SYNCHRONOUS_IO_NONALERT,
NULL, 0);
if (NT_SUCCESS(NTStatus))
{
ByteOffset.LowPart = ByteOffset.HighPart = 0;
NTStatus = ZwReadFile(FileHandle, NULL, NULL, NULL, &IOStatusBlock,
FileBuffer, BUFFER_SIZE, &ByteOffset, NULL);
if (NT_SUCCESS(NTStatus))
{
FileBuffer[BUFFER_SIZE - 1] = '\0';
DbgPrint("%s\n", FileBuffer);
for (int i = 0; i < BUFFER_SIZE; ++i)
{
outStr[i] = FileBuffer[i];
}
}
ZwClose(FileHandle);
}
}
DebugView using DbgPrint("%s\n", buffer); shows the correct output of my textfile, however when I try to convert it like:
char myStr[BUFFER_SIZE];
ZwReadFromFile(L"\\SystemRoot\\test.txt", myStr);
DbgPrint("%s\n", myStr);
It starts to act weird again.
The Reason why I have to convert the char buffer to a PCWSTR is cause I am forced to use: RtlInitUnicodeString(&myUnicode, myStr /*L"TEST"*/);
Im struggling 3 days for it now, did research on google and stackoverflow but nothing really helped me to solve this Issue on my own. I appreciate any help I can get, sorry for my english im not a native speaker.