i am confused :(

You have to look for clues in the question and also the information provided to see which model would fit. For example: If the environment is talked about then PESTEL, 5 forces. Portfolios: BCG Oursourcing: Harmon Contextual features: Balogun and Hope Hailey. Strategic evaluation: suitabiity, feasibility, acceptability. If the question gives informeation about the economy etc, part of PESTEL can be used. If it gives info about competitors, new entrants then 5 forces. There is really no other way as the model which is most suitable depends on the question detail.

well it was very helpful, one more thing if the question talks about 2 or 3 different things like part of things from Political and economic factors from pestle, threat of new entrant because of political factors like say that china is investing in pakistan due to political relationship and it also comes up with the threat to local contractors as chinese company will handle all the contract things (porter 5 forces), so can we apply part of 2 or 3 different models in one scenario ?

Yes, you can mix and match as seems appropriate. No single model ever has the monopoly on the truth.

thank u :) u are the best