its a very straight forward process.
after getting a job offer with a signed employment contract from a german employer follow these steps;

1-  first apply for long term visa in islamabad embassy. validity 90 days. visa processing time 3 - 12 weeks.
this temp visa allows you to travel and work in germany for 90 days.

2 - after arrival in germany on a 90 day visa , apply for the bluecard application in auslanderbehorde office.

simple steps for long term visa;

- book online appointment for national visa (long term) and appear for personal interview in islamabad

https://service2.diplo.de/rktermin/extern/choose_realmList.do?locationCode=isla&request_locale=en

- documents needed in islamabad embassy (original & copies) for the work visa are almost identical to long term visa (study visa) - check embassy website long term visa section.

- documents checklist (work visa);

long-term visa forms;
- application form - long-term visas
- declaration (english/urdu) form
- security questionnaire

- appointment confirmation e-mail
- employment contract
- valid passport
- photos
- computerized national id card
- cover letter
- curriculum vitae
- travel/health insurance 90 days.
- academic degrees
- previous work experience letters
- birth certificate
- recent paystubs
- bank statement
- tax papers
- long term visa fee (pk rupees cash)
- 500 pk rupees passport return cash fee.

* proof of german language skills not required.
* documents photocopies attestation not required.
* provide the no objection certificate from the current employer if possible.
* resign from current job only after visa approval.

* only after visa approval, apply for nicop card (overseas nic) and must have your passport (with work visa) stamped from protectorate of emigrants office in order to leave pakistan.

* after arrival in germany;
- do the necessary residence address registration / anmeldung in einwohnermeldeamt office within seven days of your arrival.
- within 90 days of your visa validity, book appointment in auslanderbehorde (foreigners' registration office) of your employment city for the bluecard application.  documents checklist will be provided to you with the appointment date.  application processing time 6 - 12 weeks. your current temp work visa stays vald until your bluecard application is processed.

goodluck!