How to use API in app.service.ts in Angular an use its data in the app components

I am writing a servise.ts in which used API .But when I want to use its data in a component it's undefined. I used all dependencies

app.component.ts:
constructor(private DATA: DataInfoService){}
this.DATA.ApiService()
this.Informations = this.DATA.Informations;

And

DataInfoService.ts:

@Injectable({
  providedIn: 'root'
})...
constructor(private http: HttpClient) { }
public ApiService(info: INFO): any {
    var headers = info.headers;
    this.http.post<any>(APIAddress, info.postData, { headers }).subscribe(data => { 
    this.Informations = data
 })
}

There are two ways to use app.service.ts

1. Using as observable

api.service.ts

@Injectable({
  providedIn: 'root'
})...
constructor(private http: HttpClient) { }
public ApiService(info: INFO): any {
    var headers = info.headers;
    return this.http.post<any>(APIAddress, info.postData, { headers })
}


app.component.ts:

constructor(private DATA: DataInfoService){}

ngOnInit(){
  this.DATA.ApiService().subscribe((response) => {
     console.log("Response:", response)
  }, (error) => {})
}

2. Using as promise

api.service.ts

@Injectable({
  providedIn: 'root'
})...
constructor(private http: HttpClient) { }
public ApiService(info: INFO): any {
    var headers = info.headers;
    return new Promise((resolve, reject) => {
       this.http.post<any>(APIAddress, info.postData, { headers 
       }).subscribe((response) => {
          resolve(response)
       }, (error) => {
          reject(error);
       })
    })
}


app.component.ts:

constructor(private DATA: DataInfoService){}

ngOnInit(){
  this.DATA.ApiService().then((response) => {
     console.log("Response:", response)
  }).catch((error) => {})
}