How can foreigners in Beijing check information about retirement, pensions or the calculation method for retirement?

According to Article 2 of the Notice on Issuing the "Specific Measures for Implementing the 'Beijing Basic Pension Insurance Regulations'" (Jing Lao She Yang Fa [2007] No. 21)(《关于印发《关于贯彻实施＜北京市基本养老保险规定＞有关问题的具体办法》的通知》（京劳社养发[2007]21号）), the basic pension is calculated as follows:
Basic Monthly Pension:
The standard is calculated based on the average of the city's average monthly wage in the previous year at the time of the insured's retirement and the individual's indexed average monthly contribution wage. For each full year of the insured’s total contribution period (including deemed contribution years, as below), 1% will be granted.

Monthly Personal Account Pension:
The standard is determined by dividing the total accumulated savings in the insured’s personal account by the number of months specified in the national calculation table (see Appendix 1).

Monthly Transitional Pension:
The standard is the sum of the transitional pension calculated based on deemed contribution years and the transitional pension calculated based on actual contribution years.

The document can be accessed via:
https://www.beijing.gov.cn/zhengce/zhengcefagui/qtwj/200804/t20080414_567066.html